Merge pull request #5687 from takluyver/pexpect-3.2

Update bundled pexpect to 3.2

IPython/external/pexpect/_pexpect.py

@@ -1,4 +1,4 b''
-"""Pexpect is a Python module for spawning child applications and controlling
+'''Pexpect is a Python module for spawning child applications and controlling
 them automatically. Pexpect can be used for automating interactive applications
 such as ssh, ftp, passwd, telnet, etc. It can be used to a automate setup
 scripts for duplicating software package installations on different servers. It
@@ -25,9 +25,9 b" expecting responses (waiting for patterns in the child's output)."
 
 For example::
 
-    child = pexpect.spawn('scp foo [e-mail]:.')
-    child.expect ('Password:')
-    child.sendline (mypassword)
+    child = pexpect.spawn('scp foo [e-mail]:.')
+    child.expect('Password:')
+    child.sendline(mypassword)
 
 This works even for commands that ask for passwords or other input outside of
 the normal stdio streams. For example, ssh reads input directly from the TTY
@@ -39,34 +39,34 b' vander Molen, George Todd, Noel Taylor, Nicolas D. Cesar, Alexander Gattin,'
 Jacques-Etienne Baudoux, Geoffrey Marshall, Francisco Lourenco, Glen Mabey,
 Karthik Gurusamy, Fernando Perez, Corey Minyard, Jon Cohen, Guillaume
 Chazarain, Andrew Ryan, Nick Craig-Wood, Andrew Stone, Jorgen Grahn, John
-Spiegel, Jan Grant, Shane Kerr and Thomas Kluyver. Let me know if I forgot anyone.
+Spiegel, Jan Grant, and Shane Kerr. Let me know if I forgot anyone.
 
 Pexpect is free, open source, and all that good stuff.
-
-Permission is hereby granted, free of charge, to any person obtaining a copy of
-this software and associated documentation files (the "Software"), to deal in
-the Software without restriction, including without limitation the rights to
-use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
-of the Software, and to permit persons to whom the Software is furnished to do
-so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
-
-Pexpect Copyright (c) 2008-2011 Noah Spurrier
 http://pexpect.sourceforge.net/
-"""
+
+PEXPECT LICENSE
+
+    This license is approved by the OSI and FSF as GPL-compatible.
+        http://opensource.org/licenses/isc-license.txt
+
+    Copyright (c) 2012, Noah Spurrier <[e-mail]>
+    PERMISSION TO USE, COPY, MODIFY, AND/OR DISTRIBUTE THIS SOFTWARE FOR ANY
+    PURPOSE WITH OR WITHOUT FEE IS HEREBY GRANTED, PROVIDED THAT THE ABOVE
+    COPYRIGHT NOTICE AND THIS PERMISSION NOTICE APPEAR IN ALL COPIES.
+    THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+    MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+'''
 
 try:
-    import os, sys, time
+    import os
+    import sys
+    import time
     import select
     import re
     import struct
@@ -79,97 +79,72 b' try:'
     import errno
     import traceback
     import signal
-except ImportError as e:
-    raise ImportError (str(e) + """
+    import codecs
+except ImportError:  # pragma: no cover
+    err = sys.exc_info()[1]
+    raise ImportError(str(err) + '''
 
 A critical module was not found. Probably this operating system does not
-support it. Pexpect is intended for UNIX-like operating systems.""")
+support it. Pexpect is intended for UNIX-like operating systems.''')
+
+__version__ = '3.2'
+__revision__ = ''
+__all__ = ['ExceptionPexpect', 'EOF', 'TIMEOUT', 'spawn', 'spawnu', 'run', 'runu',
+           'which', 'split_command_line', '__version__', '__revision__']
 
-__version__ = '2.6.dev'
-version = __version__
-version_info = (2,6,'dev')
-__all__ = ['ExceptionPexpect', 'EOF', 'TIMEOUT', 'spawn', 'spawnb', 'run', 'which',
-    'split_command_line', '__version__']
+PY3 = (sys.version_info[0] >= 3)
 
 # Exception classes used by this module.
 class ExceptionPexpect(Exception):
-
-    """Base class for all exceptions raised by this module.
-    """
+    '''Base class for all exceptions raised by this module.
+    '''
 
     def __init__(self, value):
-
+        super(ExceptionPexpect, self).__init__(value)
         self.value = value
 
     def __str__(self):
-
         return str(self.value)
 
     def get_trace(self):
-
-        """This returns an abbreviated stack trace with lines that only concern
+        '''This returns an abbreviated stack trace with lines that only concern
         the caller. In other words, the stack trace inside the Pexpect module
-        is not included. """
+        is not included. '''
 
         tblist = traceback.extract_tb(sys.exc_info()[2])
-        #tblist = filter(self.__filter_not_pexpect, tblist)
-        tblist = [item for item in tblist if self.__filter_not_pexpect(item)]
+        tblist = [item for item in tblist if 'pexpect/__init__' not in item[0]]
         tblist = traceback.format_list(tblist)
         return ''.join(tblist)
 
-    def __filter_not_pexpect(self, trace_list_item):
-
-        """This returns True if list item 0 the string 'pexpect.py' in it. """
-
-        if trace_list_item[0].find('pexpect.py') == -1:
-            return True
-        else:
-            return False
 
 class EOF(ExceptionPexpect):
+    '''Raised when EOF is read from a child.
+    This usually means the child has exited.'''
 
-    """Raised when EOF is read from a child. This usually means the child has exited."""
 
 class TIMEOUT(ExceptionPexpect):
-
-    """Raised when a read time exceeds the timeout. """
+    '''Raised when a read time exceeds the timeout. '''
 
 ##class TIMEOUT_PATTERN(TIMEOUT):
-##    """Raised when the pattern match time exceeds the timeout.
+##    '''Raised when the pattern match time exceeds the timeout.
 ##    This is different than a read TIMEOUT because the child process may
 ##    give output, thus never give a TIMEOUT, but the output
 ##    may never match a pattern.
-##    """
+##    '''
 ##class MAXBUFFER(ExceptionPexpect):
-##    """Raised when a scan buffer fills before matching an expected pattern."""
-
-PY3 = (sys.version_info[0] >= 3)
-
-unicode_type = str if PY3 else unicode
-basestring_type = str if PY3 else basestring
-
-def _cast_bytes(s, enc):
-    if isinstance(s, unicode_type):
-        return s.encode(enc)
-    return s
-
-def _cast_unicode(s, enc):
-    if isinstance(s, bytes):
-        return s.decode(enc)
-    return s
+##    '''Raised when a buffer fills before matching an expected pattern.'''
 
-re_type = type(re.compile(''))
 
-def run (command, timeout=-1, withexitstatus=False, events=None, extra_args=None,
-         logfile=None, cwd=None, env=None, encoding='utf-8'):
+def run(command, timeout=-1, withexitstatus=False, events=None,
+        extra_args=None, logfile=None, cwd=None, env=None):
 
-    """
+    '''
     This function runs the given command; waits for it to finish; then
     returns all output as a string. STDERR is included in output. If the full
     path to the command is not given then the path is searched.
 
     Note that lines are terminated by CR/LF (\\r\\n) combination even on
-    UNIX-like systems because this is the standard for pseudo ttys. If you set
+    UNIX-like systems because this is the standard for pseudottys. If you set
     'withexitstatus' to true, then run will return a tuple of (command_output,
     exitstatus). If 'withexitstatus' is false then this returns just
     command_output.
@@ -178,40 +153,37 b' def run (command, timeout=-1, withexitstatus=False, events=None, extra_args=None'
     For example, the following code uses spawn::
 
         from pexpect import *
-        child = spawn('scp foo [e-mail]:.')
-        child.expect ('(?i)password')
-        child.sendline (mypassword)
+        child = spawn('scp foo [e-mail]:.')
+        child.expect('(?i)password')
+        child.sendline(mypassword)
 
     The previous code can be replace with the following::
 
         from pexpect import *
-        run ('scp foo [e-mail]:.', events={'(?i)password': mypassword})
+        run('scp foo [e-mail]:.', events={'(?i)password': mypassword})
 
-    Examples
-    ========
+    **Examples**
 
     Start the apache daemon on the local machine::
 
         from pexpect import *
-        run ("/usr/local/apache/bin/apachectl start")
+        run("/usr/local/apache/bin/apachectl start")
 
     Check in a file using SVN::
 
         from pexpect import *
-        run ("svn ci -m 'automatic commit' my_file.py")
+        run("svn ci -m 'automatic commit' my_file.py")
 
     Run a command and capture exit status::
 
         from pexpect import *
-        (command_output, exitstatus) = run ('ls -l /bin', withexitstatus=1)
-
-    Tricky Examples
-    ===============
+        (command_output, exitstatus) = run('ls -l /bin', withexitstatus=1)
 
     The following will run SSH and execute 'ls -l' on the remote machine. The
     password 'secret' will be sent if the '(?i)password' pattern is ever seen::
 
-        run ("ssh [e-mail] 'ls -l'", events={'(?i)password':'secret\\n'})
+        run("ssh [e-mail] 'ls -l'",
+            events={'(?i)password':'secret\\n'})
 
     This will start mencoder to rip a video from DVD. This will also display
     progress ticks every 5 seconds as it runs. For example::
@@ -219,7 +191,8 b' def run (command, timeout=-1, withexitstatus=False, events=None, extra_args=None'
         from pexpect import *
         def print_ticks(d):
             print d['event_count'],
-        run ("mencoder dvd://1 -o video.avi -oac copy -ovc copy", events={TIMEOUT:print_ticks}, timeout=5)
+        run("mencoder dvd://1 -o video.avi -oac copy -ovc copy",
+            events={TIMEOUT:print_ticks}, timeout=5)
 
     The 'events' argument should be a dictionary of patterns and responses.
     Whenever one of the patterns is seen in the command out run() will send the
@@ -233,92 +206,126 b' def run (command, timeout=-1, withexitstatus=False, events=None, extra_args=None'
     the next event. A callback may also return a string which will be sent to
     the child. 'extra_args' is not used by directly run(). It provides a way to
     pass data to a callback function through run() through the locals
-    dictionary passed to a callback."""
+    dictionary passed to a callback.
+    '''
+    return _run(command, timeout=timeout, withexitstatus=withexitstatus,
+                events=events, extra_args=extra_args, logfile=logfile, cwd=cwd,
+                env=env, _spawn=spawn)
+
+def runu(command, timeout=-1, withexitstatus=False, events=None,
+        extra_args=None, logfile=None, cwd=None, env=None, **kwargs):
+    """This offers the same interface as :func:`run`, but using unicode.
+
+    Like :class:`spawnu`, you can pass ``encoding`` and ``errors`` parameters,
+    which will be used for both input and output.
+    """
+    return _run(command, timeout=timeout, withexitstatus=withexitstatus,
+                events=events, extra_args=extra_args, logfile=logfile, cwd=cwd,
+                env=env, _spawn=spawnu, **kwargs)
 
+def _run(command, timeout, withexitstatus, events, extra_args, logfile, cwd,
+         env, _spawn, **kwargs):
     if timeout == -1:
-        child = spawn(command, maxread=2000, logfile=logfile, cwd=cwd, env=env,
-                      encoding=encoding)
+        child = _spawn(command, maxread=2000, logfile=logfile, cwd=cwd, env=env,
+                        **kwargs)
     else:
-        child = spawn(command, timeout=timeout, maxread=2000, logfile=logfile,
-                      cwd=cwd, env=env, encoding=encoding)
+        child = _spawn(command, timeout=timeout, maxread=2000, logfile=logfile,
+                cwd=cwd, env=env, **kwargs)
     if events is not None:
-        patterns = events.keys()
-        responses = events.values()
+        patterns = list(events.keys())
+        responses = list(events.values())
     else:
-        patterns=None # We assume that EOF or TIMEOUT will save us.
-        responses=None
+        # This assumes EOF or TIMEOUT will eventually cause run to terminate.
+        patterns = None
+        responses = None
     child_result_list = []
     event_count = 0
-    while 1:
+    while True:
         try:
-            index = child.expect (patterns)
-            if isinstance(child.after, basestring_type):
+            index = child.expect(patterns)
+            if isinstance(child.after, child.allowed_string_types):
                 child_result_list.append(child.before + child.after)
-            else: # child.after may have been a TIMEOUT or EOF, so don't cat those.
+            else:
+                # child.after may have been a TIMEOUT or EOF,
+                # which we don't want appended to the list.
                 child_result_list.append(child.before)
-            if isinstance(responses[index], basestring_type):
+            if isinstance(responses[index], child.allowed_string_types):
                 child.send(responses[index])
-            elif type(responses[index]) is types.FunctionType:
+            elif isinstance(responses[index], types.FunctionType):
                 callback_result = responses[index](locals())
                 sys.stdout.flush()
-                if isinstance(callback_result, basestring_type):
+                if isinstance(callback_result, child.allowed_string_types):
                     child.send(callback_result)
                 elif callback_result:
                     break
             else:
-                raise TypeError ('The callback must be a string or function type.')
+                raise TypeError('The callback must be a string or function.')
             event_count = event_count + 1
-        except TIMEOUT as e:
+        except TIMEOUT:
             child_result_list.append(child.before)
             break
-        except EOF as e:
+        except EOF:
             child_result_list.append(child.before)
             break
-    child_result = child._empty_buffer.join(child_result_list)
+    child_result = child.string_type().join(child_result_list)
     if withexitstatus:
         child.close()
         return (child_result, child.exitstatus)
     else:
         return child_result
 
-class spawnb(object):
-    """Use this class to start and control child applications with a pure-bytes
-    interface."""
-    
-    _buffer_type = bytes
-    def _cast_buffer_type(self, s):
-        return _cast_bytes(s, self.encoding)
-    _empty_buffer = b''
-    _pty_newline = b'\r\n'
-    
-    # Some code needs this to exist, but it's mainly for the spawn subclass.
-    encoding = 'utf-8'
-
-    def __init__(self, command, args=[], timeout=30, maxread=2000, searchwindowsize=None,
-                 logfile=None, cwd=None, env=None):
-
-        """This is the constructor. The command parameter may be a string that
+class spawn(object):
+    '''This is the main class interface for Pexpect. Use this class to start
+    and control child applications. '''
+    string_type = bytes
+    if PY3:
+        allowed_string_types = (bytes, str)
+        @staticmethod
+        def _chr(c):
+            return bytes([c])
+        linesep = os.linesep.encode('ascii')
+
+        @staticmethod
+        def write_to_stdout(b):
+            try:
+                return sys.stdout.buffer.write(b)
+            except AttributeError:
+                # If stdout has been replaced, it may not have .buffer
+                return sys.stdout.write(b.decode('ascii', 'replace'))
+    else:
+        allowed_string_types = (basestring,)  # analysis:ignore
+        _chr = staticmethod(chr)
+        linesep = os.linesep
+        write_to_stdout = sys.stdout.write
+
+    encoding = None
+
+    def __init__(self, command, args=[], timeout=30, maxread=2000,
+        searchwindowsize=None, logfile=None, cwd=None, env=None,
+        ignore_sighup=True):
+
+        '''This is the constructor. The command parameter may be a string that
         includes a command and any arguments to the command. For example::
 
-            child = pexpect.spawn ('/usr/bin/ftp')
-            child = pexpect.spawn ('/usr/bin/ssh [e-mail]')
-            child = pexpect.spawn ('ls -latr /tmp')
+            child = pexpect.spawn('/usr/bin/ftp')
+            child = pexpect.spawn('/usr/bin/ssh [e-mail]')
+            child = pexpect.spawn('ls -latr /tmp')
 
         You may also construct it with a list of arguments like so::
 
-            child = pexpect.spawn ('/usr/bin/ftp', [])
-            child = pexpect.spawn ('/usr/bin/ssh', ['[e-mail]'])
-            child = pexpect.spawn ('ls', ['-latr', '/tmp'])
+            child = pexpect.spawn('/usr/bin/ftp', [])
+            child = pexpect.spawn('/usr/bin/ssh', ['[e-mail]'])
+            child = pexpect.spawn('ls', ['-latr', '/tmp'])
 
         After this the child application will be created and will be ready to
         talk to. For normal use, see expect() and send() and sendline().
 
         Remember that Pexpect does NOT interpret shell meta characters such as
-        redirect, pipe, or wild cards (>, |, or *). This is a common mistake.
-        If you want to run a command and pipe it through another command then
-        you must also start a shell. For example::
+        redirect, pipe, or wild cards (``>``, ``|``, or ``*``). This is a
+        common mistake.  If you want to run a command and pipe it through
+        another command then you must also start a shell. For example::
 
-            child = pexpect.spawn('/bin/bash -c "ls -l | grep LOG > log_list.txt"')
+            child = pexpect.spawn('/bin/bash -c "ls -l | grep LOG > logs.txt"')
             child.expect(pexpect.EOF)
 
         The second form of spawn (where you pass a list of arguments) is useful
@@ -326,7 +333,7 b' class spawnb(object):'
         argument list. This can make syntax more clear. For example, the
         following is equivalent to the previous example::
 
-            shell_cmd = 'ls -l | grep LOG > log_list.txt'
+            shell_cmd = 'ls -l | grep LOG > logs.txt'
             child = pexpect.spawn('/bin/bash', ['-c', shell_cmd])
             child.expect(pexpect.EOF)
 
@@ -337,14 +344,14 b' class spawnb(object):'
         output are read back from the child. This feature is useful in
         conjunction with searchwindowsize.
 
-        The searchwindowsize attribute sets the how far back in the incomming
+        The searchwindowsize attribute sets the how far back in the incoming
         seach buffer Pexpect will search for pattern matches. Every time
         Pexpect reads some data from the child it will append the data to the
-        incomming buffer. The default is to search from the beginning of the
-        imcomming buffer each time new data is read from the child. But this is
+        incoming buffer. The default is to search from the beginning of the
+        incoming buffer each time new data is read from the child. But this is
         very inefficient if you are running a command that generates a large
-        amount of data where you want to match The searchwindowsize does not
-        effect the size of the incomming data buffer. You will still have
+        amount of data where you want to match. The searchwindowsize does not
+        affect the size of the incoming data buffer. You will still have
         access to the full buffer after expect() returns.
 
         The logfile member turns on or off logging. All input and output will
@@ -355,7 +362,7 b' class spawnb(object):'
         Example log input and output to a file::
 
             child = pexpect.spawn('some_command')
-            fout = open('mylog.txt','w')
+            fout = file('mylog.txt','w')
             child.logfile = fout
 
         Example log to stdout::
@@ -375,6 +382,11 b' class spawnb(object):'
 
             self.logfile_send = fout
 
+        If ``ignore_sighup`` is True, the child process will ignore SIGHUP
+        signals. For now, the default is True, to preserve the behaviour of
+        earlier versions of Pexpect, but you should pass this explicitly if you
+        want to rely on it.
+
         The delaybeforesend helps overcome a weird behavior that many users
         were experiencing. The typical problem was that a user would expect() a
         "Password:" prompt and then immediately call sendline() to send the
@@ -403,7 +415,7 b' class spawnb(object):'
         signalstatus will store the signal value and exitstatus will be None.
         If you need more detail you can also read the self.status member which
         stores the status returned by os.waitpid. You can interpret this using
-        os.WIFEXITED/os.WEXITSTATUS or os.WIFSIGNALED/os.TERMSIG. """
+        os.WIFEXITED/os.WEXITSTATUS or os.WIFSIGNALED/os.TERMSIG. '''
 
         self.STDIN_FILENO = pty.STDIN_FILENO
         self.STDOUT_FILENO = pty.STDOUT_FILENO
@@ -421,76 +433,104 b' class spawnb(object):'
         self.terminated = True
         self.exitstatus = None
         self.signalstatus = None
-        self.status = None # status returned by os.waitpid
+        # status returned by os.waitpid
+        self.status = None
         self.flag_eof = False
         self.pid = None
-        self.child_fd = -1 # initially closed
+        # the chile filedescriptor is initially closed
+        self.child_fd = -1
         self.timeout = timeout
         self.delimiter = EOF
         self.logfile = logfile
-        self.logfile_read = None # input from child (read_nonblocking)
-        self.logfile_send = None # output to send (send, sendline)
-        self.maxread = maxread # max bytes to read at one time into buffer
-        self.buffer = self._empty_buffer # This is the read buffer. See maxread.
-        self.searchwindowsize = searchwindowsize # Anything before searchwindowsize point is preserved, but not searched.
-        # Most Linux machines don't like delaybeforesend to be below 0.03 (30 ms).
-        self.delaybeforesend = 0.05 # Sets sleep time used just before sending data to child. Time in seconds.
-        self.delayafterclose = 0.1 # Sets delay in close() method to allow kernel time to update process status. Time in seconds.
-        self.delayafterterminate = 0.1 # Sets delay in terminate() method to allow kernel time to update process status. Time in seconds.
-        self.softspace = False # File-like object.
-        self.name = '<' + repr(self) + '>' # File-like object.
-        self.closed = True # File-like object.
+        # input from child (read_nonblocking)
+        self.logfile_read = None
+        # output to send (send, sendline)
+        self.logfile_send = None
+        # max bytes to read at one time into buffer
+        self.maxread = maxread
+        # This is the read buffer. See maxread.
+        self.buffer = self.string_type()
+        # Data before searchwindowsize point is preserved, but not searched.
+        self.searchwindowsize = searchwindowsize
+        # Delay used before sending data to child. Time in seconds.
+        # Most Linux machines don't like this to be below 0.03 (30 ms).
+        self.delaybeforesend = 0.05
+        # Used by close() to give kernel time to update process status.
+        # Time in seconds.
+        self.delayafterclose = 0.1
+        # Used by terminate() to give kernel time to update process status.
+        # Time in seconds.
+        self.delayafterterminate = 0.1
+        self.softspace = False
+        self.name = '<' + repr(self) + '>'
+        self.closed = True
         self.cwd = cwd
         self.env = env
-        self.__irix_hack = (sys.platform.lower().find('irix')>=0) # This flags if we are running on irix
+        self.ignore_sighup = ignore_sighup
+        # This flags if we are running on irix
+        self.__irix_hack = (sys.platform.lower().find('irix') >= 0)
         # Solaris uses internal __fork_pty(). All others use pty.fork().
-        if 'solaris' in sys.platform.lower() or 'sunos5' in sys.platform.lower():
+        if ((sys.platform.lower().find('solaris') >= 0)
+            or (sys.platform.lower().find('sunos5') >= 0)):
             self.use_native_pty_fork = False
         else:
             self.use_native_pty_fork = True
 
-
-        # allow dummy instances for subclasses that may not use command or args.
+        # Support subclasses that do not use command or args.
         if command is None:
             self.command = None
             self.args = None
             self.name = '<pexpect factory incomplete>'
         else:
-            self._spawn (command, args)
+            self._spawn(command, args)
 
-    def __del__(self):
+    @staticmethod
+    def _coerce_expect_string(s):
+        if not isinstance(s, bytes):
+            return s.encode('ascii')
+        return s
+
+    @staticmethod
+    def _coerce_send_string(s):
+        if not isinstance(s, bytes):
+            return s.encode('utf-8')
+        return s
 
-        """This makes sure that no system resources are left open. Python only
+    @staticmethod
+    def _coerce_read_string(s):
+        return s
+
+    def __del__(self):
+        '''This makes sure that no system resources are left open. Python only
         garbage collects Python objects. OS file descriptors are not Python
         objects, so they must be handled explicitly. If the child file
         descriptor was opened outside of this class (passed to the constructor)
-        then this does not close it. """
+        then this does not close it. '''
 
         if not self.closed:
             # It is possible for __del__ methods to execute during the
             # teardown of the Python VM itself. Thus self.close() may
             # trigger an exception because os.close may be None.
-            # -- Fernando Perez
             try:
                 self.close()
+            # which exception, shouldnt' we catch explicitly .. ?
             except:
                 pass
 
     def __str__(self):
-
-        """This returns a human-readable string that represents the state of
-        the object. """
+        '''This returns a human-readable string that represents the state of
+        the object. '''
 
         s = []
         s.append(repr(self))
         s.append('version: ' + __version__)
         s.append('command: ' + str(self.command))
-        s.append('args: ' + str(self.args))
-        s.append('searcher: ' + str(self.searcher))
-        s.append('buffer (last 100 chars): ' + str(self.buffer)[-100:])
-        s.append('before (last 100 chars): ' + str(self.before)[-100:])
-        s.append('after: ' + str(self.after))
-        s.append('match: ' + str(self.match))
+        s.append('args: %r' % (self.args,))
+        s.append('searcher: %r' % (self.searcher,))
+        s.append('buffer (last 100 chars): %r' % (self.buffer)[-100:],)
+        s.append('before (last 100 chars): %r' % (self.before)[-100:],)
+        s.append('after: %r' % (self.after,))
+        s.append('match: %r' % (self.match,))
         s.append('match_index: ' + str(self.match_index))
         s.append('exitstatus: ' + str(self.exitstatus))
         s.append('flag_eof: ' + str(self.flag_eof))
@@ -510,12 +550,11 b' class spawnb(object):'
         s.append('delayafterterminate: ' + str(self.delayafterterminate))
         return '\n'.join(s)
 
-    def _spawn(self,command,args=[]):
-
-        """This starts the given command in a child process. This does all the
+    def _spawn(self, command, args=[]):
+        '''This starts the given command in a child process. This does all the
         fork/exec type of stuff for a pty. This is called by __init__. If args
         is empty then command will be parsed (split on spaces) and args will be
-        set to parsed arguments. """
+        set to parsed arguments. '''
 
         # The pid and child_fd of this object get set by this method.
         # Note that it is difficult for this method to fail.
@@ -523,47 +562,57 b' class spawnb(object):'
         # So the only way you can tell if the child process started
         # or not is to try to read from the file descriptor. If you get
         # EOF immediately then it means that the child is already dead.
-        # That may not necessarily be bad because you may haved spawned a child
+        # That may not necessarily be bad because you may have spawned a child
         # that performs some task; creates no stdout output; and then dies.
 
         # If command is an int type then it may represent a file descriptor.
-        if type(command) == type(0):
-            raise ExceptionPexpect ('Command is an int type. If this is a file descriptor then maybe you want to use fdpexpect.fdspawn which takes an existing file descriptor instead of a command string.')
+        if isinstance(command, type(0)):
+            raise ExceptionPexpect('Command is an int type. ' +
+                    'If this is a file descriptor then maybe you want to ' +
+                    'use fdpexpect.fdspawn which takes an existing ' +
+                    'file descriptor instead of a command string.')
 
-        if type (args) != type([]):
-            raise TypeError ('The argument, args, must be a list.')
+        if not isinstance(args, type([])):
+            raise TypeError('The argument, args, must be a list.')
 
         if args == []:
             self.args = split_command_line(command)
             self.command = self.args[0]
         else:
-            self.args = args[:] # work with a copy
-            self.args.insert (0, command)
+            # Make a shallow copy of the args list.
+            self.args = args[:]
+            self.args.insert(0, command)
             self.command = command
 
         command_with_path = which(self.command)
         if command_with_path is None:
-            raise ExceptionPexpect ('The command was not found or was not executable: %s.' % self.command)
+            raise ExceptionPexpect('The command was not found or was not ' +
+                    'executable: %s.' % self.command)
         self.command = command_with_path
         self.args[0] = self.command
 
-        self.name = '<' + ' '.join (self.args) + '>'
+        self.name = '<' + ' '.join(self.args) + '>'
 
-        assert self.pid is None, 'The pid member should be None.'
-        assert self.command is not None, 'The command member should not be None.'
+        assert self.pid is None, 'The pid member must be None.'
+        assert self.command is not None, 'The command member must not be None.'
 
         if self.use_native_pty_fork:
             try:
                 self.pid, self.child_fd = pty.fork()
-            except OSError as e:
-                raise ExceptionPexpect('Error! pty.fork() failed: ' + str(e))
-        else: # Use internal __fork_pty
+            except OSError:
+                err = sys.exc_info()[1]
+                raise ExceptionPexpect('pty.fork() failed: ' + str(err))
+        else:
+            # Use internal __fork_pty
             self.pid, self.child_fd = self.__fork_pty()
 
-        if self.pid == 0: # Child
+        if self.pid == 0:
+            # Child
             try:
-                self.child_fd = sys.stdout.fileno() # used by setwinsize()
+                # used by setwinsize()
+                self.child_fd = sys.stdout.fileno()
                 self.setwinsize(24, 80)
+            # which exception, shouldnt' we catch explicitly .. ?
             except:
                 # Some platforms do not like setwinsize (Cygwin).
                 # This will cause problem when running applications that
@@ -572,16 +621,14 b' class spawnb(object):'
                 pass
             # Do not allow child to inherit open file descriptors from parent.
             max_fd = resource.getrlimit(resource.RLIMIT_NOFILE)[0]
-            for i in range (3, max_fd):
+            for i in range(3, max_fd):
                 try:
-                    os.close (i)
+                    os.close(i)
                 except OSError:
                     pass
 
-            # I don't know why this works, but ignoring SIGHUP fixes a
-            # problem when trying to start a Java daemon with sudo
-            # (specifically, Tomcat).
-            signal.signal(signal.SIGHUP, signal.SIG_IGN)
+            if self.ignore_sighup:
+                signal.signal(signal.SIGHUP, signal.SIG_IGN)
 
             if self.cwd is not None:
                 os.chdir(self.cwd)
@@ -595,8 +642,7 b' class spawnb(object):'
         self.closed = False
 
     def __fork_pty(self):
-
-        """This implements a substitute for the forkpty system call. This
+        '''This implements a substitute for the forkpty system call. This
         should be more portable than the pty.fork() function. Specifically,
         this should work on Solaris.
 
@@ -607,15 +653,15 b' class spawnb(object):'
 
             http://mail.python.org/pipermail/python-dev/2003-May/035281.html
 
-        """
+        '''
 
         parent_fd, child_fd = os.openpty()
         if parent_fd < 0 or child_fd < 0:
-            raise ExceptionPexpect("Error! Could not open pty with os.openpty().")
+            raise ExceptionPexpect("Could not open with os.openpty().")
 
         pid = os.fork()
         if pid < 0:
-            raise ExceptionPexpect("Error! Failed os.fork().")
+            raise ExceptionPexpect("Failed os.fork().")
         elif pid == 0:
             # Child.
             os.close(parent_fd)
@@ -634,18 +680,18 b' class spawnb(object):'
         return pid, parent_fd
 
     def __pty_make_controlling_tty(self, tty_fd):
-
-        """This makes the pseudo-terminal the controlling tty. This should be
+        '''This makes the pseudo-terminal the controlling tty. This should be
         more portable than the pty.fork() function. Specifically, this should
-        work on Solaris. """
+        work on Solaris. '''
 
         child_name = os.ttyname(tty_fd)
 
         # Disconnect from controlling tty. Harmless if not already connected.
         try:
-            fd = os.open("/dev/tty", os.O_RDWR | os.O_NOCTTY);
+            fd = os.open("/dev/tty", os.O_RDWR | os.O_NOCTTY)
             if fd >= 0:
                 os.close(fd)
+        # which exception, shouldnt' we catch explicitly .. ?
         except:
             # Already disconnected. This happens if running inside cron.
             pass
@@ -655,71 +701,68 b' class spawnb(object):'
         # Verify we are disconnected from controlling tty
         # by attempting to open it again.
         try:
-            fd = os.open("/dev/tty", os.O_RDWR | os.O_NOCTTY);
+            fd = os.open("/dev/tty", os.O_RDWR | os.O_NOCTTY)
             if fd >= 0:
                 os.close(fd)
-                raise ExceptionPexpect("Error! Failed to disconnect from controlling tty. It is still possible to open /dev/tty.")
+                raise ExceptionPexpect('Failed to disconnect from ' +
+                    'controlling tty. It is still possible to open /dev/tty.')
+        # which exception, shouldnt' we catch explicitly .. ?
         except:
             # Good! We are disconnected from a controlling tty.
             pass
 
         # Verify we can open child pty.
-        fd = os.open(child_name, os.O_RDWR);
+        fd = os.open(child_name, os.O_RDWR)
         if fd < 0:
-            raise ExceptionPexpect("Error! Could not open child pty, " + child_name)
+            raise ExceptionPexpect("Could not open child pty, " + child_name)
         else:
             os.close(fd)
 
         # Verify we now have a controlling tty.
         fd = os.open("/dev/tty", os.O_WRONLY)
         if fd < 0:
-            raise ExceptionPexpect("Error! Could not open controlling tty, /dev/tty")
+            raise ExceptionPexpect("Could not open controlling tty, /dev/tty")
         else:
             os.close(fd)
 
-    def fileno (self):   # File-like object.
-
-        """This returns the file descriptor of the pty for the child.
-        """
-
+    def fileno(self):
+        '''This returns the file descriptor of the pty for the child.
+        '''
         return self.child_fd
 
-    def close (self, force=True):   # File-like object.
-
-        """This closes the connection with the child application. Note that
+    def close(self, force=True):
+        '''This closes the connection with the child application. Note that
         calling close() more than once is valid. This emulates standard Python
         behavior with files. Set force to True if you want to make sure that
         the child is terminated (SIGKILL is sent if the child ignores SIGHUP
-        and SIGINT). """
+        and SIGINT). '''
 
         if not self.closed:
             self.flush()
-            os.close (self.child_fd)
-            time.sleep(self.delayafterclose) # Give kernel time to update process status.
+            os.close(self.child_fd)
+            # Give kernel time to update process status.
+            time.sleep(self.delayafterclose)
             if self.isalive():
                 if not self.terminate(force):
-                    raise ExceptionPexpect ('close() could not terminate the child using terminate()')
+                    raise ExceptionPexpect('Could not terminate the child.')
             self.child_fd = -1
             self.closed = True
             #self.pid = None
 
-    def flush (self):   # File-like object.
-
-        """This does nothing. It is here to support the interface for a
-        File-like object. """
+    def flush(self):
+        '''This does nothing. It is here to support the interface for a
+        File-like object. '''
 
         pass
 
-    def isatty (self):   # File-like object.
-
-        """This returns True if the file descriptor is open and connected to a
-        tty(-like) device, else False. """
+    def isatty(self):
+        '''This returns True if the file descriptor is open and connected to a
+        tty(-like) device, else False. '''
 
         return os.isatty(self.child_fd)
 
-    def waitnoecho (self, timeout=-1):
-
-        """This waits until the terminal ECHO flag is set False. This returns
+    def waitnoecho(self, timeout=-1):
+        '''This waits until the terminal ECHO flag is set False. This returns
         True if the echo mode is off. This returns False if the ECHO flag was
         not set False before the timeout. This can be used to detect when the
         child is waiting for a password. Usually a child application will turn
@@ -727,13 +770,13 b' class spawnb(object):'
         example, instead of expecting the "password:" prompt you can wait for
         the child to set ECHO off::
 
-            p = pexpect.spawn ('ssh [e-mail]')
+            p = pexpect.spawn('ssh [e-mail]')
             p.waitnoecho()
             p.sendline(mypassword)
 
         If timeout==-1 then this method will use the value in self.timeout.
         If timeout==None then this method to block until ECHO flag is False.
-        """
+        '''
 
         if timeout == -1:
             timeout = self.timeout
@@ -748,47 +791,45 b' class spawnb(object):'
                 timeout = end_time - time.time()
             time.sleep(0.1)
 
-    def getecho (self):
-
-        """This returns the terminal echo mode. This returns True if echo is
+    def getecho(self):
+        '''This returns the terminal echo mode. This returns True if echo is
         on or False if echo is off. Child applications that are expecting you
-        to enter a password often set ECHO False. See waitnoecho(). """
+        to enter a password often set ECHO False. See waitnoecho(). '''
 
         attr = termios.tcgetattr(self.child_fd)
         if attr[3] & termios.ECHO:
             return True
         return False
 
-    def setecho (self, state):
-
-        """This sets the terminal echo mode on or off. Note that anything the
+    def setecho(self, state):
+        '''This sets the terminal echo mode on or off. Note that anything the
         child sent before the echo will be lost, so you should be sure that
         your input buffer is empty before you call setecho(). For example, the
         following will work as expected::
 
-            p = pexpect.spawn('cat')
-            p.sendline ('1234') # We will see this twice (once from tty echo and again from cat).
-            p.expect (['1234'])
-            p.expect (['1234'])
+            p = pexpect.spawn('cat') # Echo is on by default.
+            p.sendline('1234') # We expect see this twice from the child...
+            p.expect(['1234']) # ... once from the tty echo...
+            p.expect(['1234']) # ... and again from cat itself.
             p.setecho(False) # Turn off tty echo
-            p.sendline ('abcd') # We will set this only once (echoed by cat).
-            p.sendline ('wxyz') # We will set this only once (echoed by cat)
-            p.expect (['abcd'])
-            p.expect (['wxyz'])
+            p.sendline('abcd') # We will set this only once (echoed by cat).
+            p.sendline('wxyz') # We will set this only once (echoed by cat)
+            p.expect(['abcd'])
+            p.expect(['wxyz'])
 
         The following WILL NOT WORK because the lines sent before the setecho
         will be lost::
 
             p = pexpect.spawn('cat')
-            p.sendline ('1234') # We will see this twice (once from tty echo and again from cat).
+            p.sendline('1234')
             p.setecho(False) # Turn off tty echo
-            p.sendline ('abcd') # We will set this only once (echoed by cat).
-            p.sendline ('wxyz') # We will set this only once (echoed by cat)
-            p.expect (['1234'])
-            p.expect (['1234'])
-            p.expect (['abcd'])
-            p.expect (['wxyz'])
-        """
+            p.sendline('abcd') # We will set this only once (echoed by cat).
+            p.sendline('wxyz') # We will set this only once (echoed by cat)
+            p.expect(['1234'])
+            p.expect(['1234'])
+            p.expect(['abcd'])
+            p.expect(['wxyz'])
+        '''
 
         self.child_fd
         attr = termios.tcgetattr(self.child_fd)
@@ -796,22 +837,31 b' class spawnb(object):'
             attr[3] = attr[3] | termios.ECHO
         else:
             attr[3] = attr[3] & ~termios.ECHO
-        # I tried TCSADRAIN and TCSAFLUSH, but these were inconsistent
-        # and blocked on some platforms. TCSADRAIN is probably ideal if it worked.
+        # I tried TCSADRAIN and TCSAFLUSH, but
+        # these were inconsistent and blocked on some platforms.
+        # TCSADRAIN would probably be ideal if it worked.
         termios.tcsetattr(self.child_fd, termios.TCSANOW, attr)
 
-    def read_nonblocking (self, size = 1, timeout = -1):
+    def _log(self, s, direction):
+        if self.logfile is not None:
+            self.logfile.write(s)
+            self.logfile.flush()
+        second_log = self.logfile_send if (direction=='send') else self.logfile_read
+        if second_log is not None:
+            second_log.write(s)
+            second_log.flush()
 
-        """This reads at most size bytes from the child application. It
+    def read_nonblocking(self, size=1, timeout=-1):
+        '''This reads at most size characters from the child application. It
         includes a timeout. If the read does not complete within the timeout
         period then a TIMEOUT exception is raised. If the end of file is read
         then an EOF exception will be raised. If a log file was set using
         setlog() then all data will also be written to the log file.
 
-        If timeout is None then the read may block indefinitely. If timeout is -1
-        then the self.timeout value is used. If timeout is 0 then the child is
-        polled and if there was no data immediately ready then this will raise
-        a TIMEOUT exception.
+        If timeout is None then the read may block indefinitely.
+        If timeout is -1 then the self.timeout value is used. If timeout is 0
+        then the child is polled and if there is no data immediately ready
+        then this will raise a TIMEOUT exception.
 
         The timeout refers only to the amount of time to read at least one
         character. This is not effected by the 'size' parameter, so if you call
@@ -820,10 +870,10 b' class spawnb(object):'
         It will not wait for 30 seconds for another 99 characters to come in.
 
         This is a wrapper around os.read(). It uses select.select() to
-        implement the timeout. """
+        implement the timeout. '''
 
         if self.closed:
-            raise ValueError ('I/O operation on closed file in read_nonblocking().')
+            raise ValueError('I/O operation on closed file.')
 
         if timeout == -1:
             timeout = self.timeout
@@ -834,62 +884,62 b' class spawnb(object):'
         # For this case, I test isalive() before doing any reading.
         # If isalive() is false, then I pretend that this is the same as EOF.
         if not self.isalive():
-            r,w,e = self.__select([self.child_fd], [], [], 0) # timeout of 0 means "poll"
+            # timeout of 0 means "poll"
+            r, w, e = self.__select([self.child_fd], [], [], 0)
             if not r:
                 self.flag_eof = True
-                raise EOF ('End Of File (EOF) in read_nonblocking(). Braindead platform.')
+                raise EOF('End Of File (EOF). Braindead platform.')
         elif self.__irix_hack:
-            # This is a hack for Irix. It seems that Irix requires a long delay before checking isalive.
-            # This adds a 2 second delay, but only when the child is terminated.
+            # Irix takes a long time before it realizes a child was terminated.
+            # FIXME So does this mean Irix systems are forced to always have
+            # FIXME a 2 second delay when calling read_nonblocking? That sucks.
             r, w, e = self.__select([self.child_fd], [], [], 2)
             if not r and not self.isalive():
                 self.flag_eof = True
-                raise EOF ('End Of File (EOF) in read_nonblocking(). Pokey platform.')
+                raise EOF('End Of File (EOF). Slow platform.')
 
-        r,w,e = self.__select([self.child_fd], [], [], timeout)
+        r, w, e = self.__select([self.child_fd], [], [], timeout)
 
         if not r:
             if not self.isalive():
-                # Some platforms, such as Irix, will claim that their processes are alive;
-                # then timeout on the select; and then finally admit that they are not alive.
+                # Some platforms, such as Irix, will claim that their
+                # processes are alive; timeout on the select; and
+                # then finally admit that they are not alive.
                 self.flag_eof = True
-                raise EOF ('End of File (EOF) in read_nonblocking(). Very pokey platform.')
+                raise EOF('End of File (EOF). Very slow platform.')
             else:
-                raise TIMEOUT ('Timeout exceeded in read_nonblocking().')
+                raise TIMEOUT('Timeout exceeded.')
 
         if self.child_fd in r:
             try:
                 s = os.read(self.child_fd, size)
-            except OSError as e: # Linux does this
+            except OSError:
+                # Linux does this
                 self.flag_eof = True
-                raise EOF ('End Of File (EOF) in read_nonblocking(). Exception style platform.')
-            if s == b'': # BSD style
+                raise EOF('End Of File (EOF). Exception style platform.')
+            if s == b'':
+                # BSD style
                 self.flag_eof = True
-                raise EOF ('End Of File (EOF) in read_nonblocking(). Empty string style platform.')
-
-            s2 = self._cast_buffer_type(s)
-            if self.logfile is not None:
-                self.logfile.write(s2)
-                self.logfile.flush()
-            if self.logfile_read is not None:
-                self.logfile_read.write(s2)
-                self.logfile_read.flush()
+                raise EOF('End Of File (EOF). Empty string style platform.')
 
+            s = self._coerce_read_string(s)
+            self._log(s, 'read')
             return s
 
-        raise ExceptionPexpect ('Reached an unexpected state in read_nonblocking().')
+        raise ExceptionPexpect('Reached an unexpected state.')
 
-    def read (self, size = -1):         # File-like object.
-        """This reads at most "size" bytes from the file (less if the read hits
+    def read(self, size=-1):
+        '''This reads at most "size" bytes from the file (less if the read hits
         EOF before obtaining size bytes). If the size argument is negative or
         omitted, read all data until EOF is reached. The bytes are returned as
         a string object. An empty string is returned when EOF is encountered
-        immediately. """
+        immediately. '''
 
         if size == 0:
-            return self._empty_buffer
+            return self.string_type()
         if size < 0:
-            self.expect (self.delimiter) # delimiter default is EOF
+            # delimiter default is EOF
+            self.expect(self.delimiter)
             return self.before
 
         # I could have done this more directly by not using expect(), but
@@ -899,57 +949,47 b' class spawnb(object):'
         # worry about if I have to later modify read() or expect().
         # Note, it's OK if size==-1 in the regex. That just means it
         # will never match anything in which case we stop only on EOF.
-        if self._buffer_type is bytes:
-            pat = (u'.{%d}' % size).encode('ascii')
-        else:
-            pat = u'.{%d}' % size
-        cre = re.compile(pat, re.DOTALL)
-        index = self.expect ([cre, self.delimiter]) # delimiter default is EOF
+        cre = re.compile(self._coerce_expect_string('.{%d}' % size), re.DOTALL)
+        # delimiter default is EOF
+        index = self.expect([cre, self.delimiter])
         if index == 0:
-            return self.after ### self.before should be ''. Should I assert this?
+            ### FIXME self.before should be ''. Should I assert this?
+            return self.after
         return self.before
 
-    def readline(self, size = -1):
-        """This reads and returns one entire line. A trailing newline is kept
-        in the string, but may be absent when a file ends with an incomplete
-        line. Note: This readline() looks for a \\r\\n pair even on UNIX
-        because this is what the pseudo tty device returns. So contrary to what
-        you may expect you will receive the newline as \\r\\n. An empty string
-        is returned when EOF is hit immediately. Currently, the size argument is
-        mostly ignored, so this behavior is not standard for a file-like
-        object. If size is 0 then an empty string is returned. """
+    def readline(self, size=-1):
+        '''This reads and returns one entire line. The newline at the end of
+        line is returned as part of the string, unless the file ends without a
+        newline. An empty string is returned if EOF is encountered immediately.
+        This looks for a newline as a CR/LF pair (\\r\\n) even on UNIX because
+        this is what the pseudotty device returns. So contrary to what you may
+        expect you will receive newlines as \\r\\n.
+
+        If the size argument is 0 then an empty string is returned. In all
+        other cases the size argument is ignored, which is not standard
+        behavior for a file-like object. '''
 
         if size == 0:
-            return self._empty_buffer
-        index = self.expect ([self._pty_newline, self.delimiter]) # delimiter default is EOF
+            return self.string_type()
+        # delimiter default is EOF
+        index = self.expect([b'\r\n', self.delimiter])
         if index == 0:
-            return self.before + self._pty_newline
-        return self.before
-
-    def __iter__ (self):    # File-like object.
-
-        """This is to support iterators over a file-like object.
-        """
-
-        return self
-
-    def __next__ (self):    # File-like object.
-
-        """This is to support iterators over a file-like object.
-        """
-
-        result = self.readline()
-        if result == self._empty_buffer:
-            raise StopIteration
-        return result
-
-    if not PY3:
-        next = __next__    # File-like object.
+            return self.before + b'\r\n'
+        else:
+            return self.before
 
-    def readlines (self, sizehint = -1):    # File-like object.
+    def __iter__(self):
+        '''This is to support iterators over a file-like object.
+        '''
+        return iter(self.readline, self.string_type())
 
-        """This reads until EOF using readline() and returns a list containing
-        the lines thus read. The optional "sizehint" argument is ignored. """
+    def readlines(self, sizehint=-1):
+        '''This reads until EOF using readline() and returns a list containing
+        the lines thus read. The optional 'sizehint' argument is ignored.
+        Remember, because this reads until EOF that means the child
+        process should have closed its stdout. If you run this method on
+        a child that is still running with its stdout open then this
+        method will block until it timesout.'''
 
         lines = []
         while True:
@@ -959,86 +999,81 b' class spawnb(object):'
             lines.append(line)
         return lines
 
-    def write(self, s):   # File-like object.
-
-        """This is similar to send() except that there is no return value.
-        """
-
-        self.send (s)
+    def write(self, s):
+        '''This is similar to send() except that there is no return value.
+        '''
 
-    def writelines (self, sequence):   # File-like object.
+        self.send(s)
 
-        """This calls write() for each element in the sequence. The sequence
+    def writelines(self, sequence):
+        '''This calls write() for each element in the sequence. The sequence
         can be any iterable object producing strings, typically a list of
-        strings. This does not add line separators There is no return value.
-        """
+        strings. This does not add line separators. There is no return value.
+        '''
 
         for s in sequence:
-            self.write (s)
+            self.write(s)
 
     def send(self, s):
-
-        """This sends a string to the child process. This returns the number of
-        bytes written. If a log file was set then the data is also written to
-        the log. """
+        '''Sends string ``s`` to the child process, returning the number of
+        bytes written. If a logfile is specified, a copy is written to that
+        log. '''
 
         time.sleep(self.delaybeforesend)
-        
-        s2 = self._cast_buffer_type(s)
-        if self.logfile is not None:
-            self.logfile.write(s2)
-            self.logfile.flush()
-        if self.logfile_send is not None:
-            self.logfile_send.write(s2)
-            self.logfile_send.flush()
-        c = os.write (self.child_fd, _cast_bytes(s, self.encoding))
-        return c
 
-    def sendline(self, s=''):
+        s = self._coerce_send_string(s)
+        self._log(s, 'send')
+
+        return self._send(s)
 
-        """This is like send(), but it adds a line feed (os.linesep). This
-        returns the number of bytes written. """
+    def _send(self, s):
+        return os.write(self.child_fd, s)
+
+    def sendline(self, s=''):
+        '''Wraps send(), sending string ``s`` to child process, with os.linesep
+        automatically appended. Returns number of bytes written. '''
 
-        n = self.send (s)
-        n = n + self.send (os.linesep)
+        n = self.send(s)
+        n = n + self.send(self.linesep)
         return n
 
     def sendcontrol(self, char):
 
-        """This sends a control character to the child such as Ctrl-C or
-        Ctrl-D. For example, to send a Ctrl-G (ASCII 7)::
+        '''Helper method that wraps send() with mnemonic access for sending control
+        character to the child (such as Ctrl-C or Ctrl-D).  For example, to send
+        Ctrl-G (ASCII 7, bell, '\a')::
 
             child.sendcontrol('g')
 
         See also, sendintr() and sendeof().
-        """
+        '''
 
         char = char.lower()
         a = ord(char)
-        if a>=97 and a<=122:
+        if a >= 97 and a <= 122:
             a = a - ord('a') + 1
-            return self.send (chr(a))
-        d = {'@':0, '`':0,
-            '[':27, '{':27,
-            '\\':28, '|':28,
-            ']':29, '}': 29,
-            '^':30, '~':30,
-            '_':31,
-            '?':127}
+            return self.send(self._chr(a))
+        d = {'@': 0, '`': 0,
+            '[': 27, '{': 27,
+            '\\': 28, '|': 28,
+            ']': 29, '}': 29,
+            '^': 30, '~': 30,
+            '_': 31,
+            '?': 127}
         if char not in d:
             return 0
-        return self.send (chr(d[char]))
+        return self.send(self._chr(d[char]))
 
     def sendeof(self):
 
-        """This sends an EOF to the child. This sends a character which causes
+        '''This sends an EOF to the child. This sends a character which causes
         the pending parent output buffer to be sent to the waiting child
         program without waiting for end-of-line. If it is the first character
         of the line, the read() in the user program returns 0, which signifies
         end-of-file. This means to work as expected a sendeof() has to be
         called at the beginning of a line. This method does not send a newline.
         It is the responsibility of the caller to ensure the eof is sent at the
-        beginning of a line. """
+        beginning of a line. '''
 
         ### Hmmm... how do I send an EOF?
         ###C  if ((m = write(pty, *buf, p - *buf)) < 0)
@@ -1046,48 +1081,48 b' class spawnb(object):'
         #fd = sys.stdin.fileno()
         #old = termios.tcgetattr(fd) # remember current state
         #attr = termios.tcgetattr(fd)
-        #attr[3] = attr[3] | termios.ICANON # ICANON must be set to recognize EOF
+        #attr[3] = attr[3] | termios.ICANON # ICANON must be set to see EOF
         #try: # use try/finally to ensure state gets restored
         #    termios.tcsetattr(fd, termios.TCSADRAIN, attr)
         #    if hasattr(termios, 'CEOF'):
-        #        os.write (self.child_fd, '%c' % termios.CEOF)
+        #        os.write(self.child_fd, '%c' % termios.CEOF)
         #    else:
         #        # Silly platform does not define CEOF so assume CTRL-D
-        #        os.write (self.child_fd, '%c' % 4)
+        #        os.write(self.child_fd, '%c' % 4)
         #finally: # restore state
         #    termios.tcsetattr(fd, termios.TCSADRAIN, old)
         if hasattr(termios, 'VEOF'):
-            char = termios.tcgetattr(self.child_fd)[6][termios.VEOF]
+            char = ord(termios.tcgetattr(self.child_fd)[6][termios.VEOF])
         else:
             # platform does not define VEOF so assume CTRL-D
-            char = chr(4)
-        self.send(char)
+            char = 4
+        self.send(self._chr(char))
 
     def sendintr(self):
 
-        """This sends a SIGINT to the child. It does not require
-        the SIGINT to be the first character on a line. """
+        '''This sends a SIGINT to the child. It does not require
+        the SIGINT to be the first character on a line. '''
 
         if hasattr(termios, 'VINTR'):
-            char = termios.tcgetattr(self.child_fd)[6][termios.VINTR]
+            char = ord(termios.tcgetattr(self.child_fd)[6][termios.VINTR])
         else:
             # platform does not define VINTR so assume CTRL-C
-            char = chr(3)
-        self.send (char)
+            char = 3
+        self.send(self._chr(char))
 
-    def eof (self):
+    def eof(self):
 
-        """This returns True if the EOF exception was ever raised.
-        """
+        '''This returns True if the EOF exception was ever raised.
+        '''
 
         return self.flag_eof
 
     def terminate(self, force=False):
 
-        """This forces a child process to terminate. It starts nicely with
+        '''This forces a child process to terminate. It starts nicely with
         SIGHUP and SIGINT. If "force" is True then moves onto SIGKILL. This
         returns True if the child was terminated. This returns False if the
-        child could not be terminated. """
+        child could not be terminated. '''
 
         if not self.isalive():
             return True
@@ -1112,7 +1147,7 b' class spawnb(object):'
                 else:
                     return False
             return False
-        except OSError as e:
+        except OSError:
             # I think there are kernel timing issues that sometimes cause
             # this to happen. I think isalive() reports True, but the
             # process is dead to the kernel.
@@ -1125,107 +1160,136 b' class spawnb(object):'
 
     def wait(self):
 
-        """This waits until the child exits. This is a blocking call. This will
+        '''This waits until the child exits. This is a blocking call. This will
         not read any data from the child, so this will block forever if the
         child has unread output and has terminated. In other words, the child
-        may have printed output then called exit(); but, technically, the child
-        is still alive until its output is read. """
+        may have printed output then called exit(), but, the child is
+        technically still alive until its output is read by the parent. '''
 
         if self.isalive():
             pid, status = os.waitpid(self.pid, 0)
         else:
-            raise ExceptionPexpect ('Cannot wait for dead child process.')
+            raise ExceptionPexpect('Cannot wait for dead child process.')
         self.exitstatus = os.WEXITSTATUS(status)
-        if os.WIFEXITED (status):
+        if os.WIFEXITED(status):
             self.status = status
             self.exitstatus = os.WEXITSTATUS(status)
             self.signalstatus = None
             self.terminated = True
-        elif os.WIFSIGNALED (status):
+        elif os.WIFSIGNALED(status):
             self.status = status
             self.exitstatus = None
             self.signalstatus = os.WTERMSIG(status)
             self.terminated = True
-        elif os.WIFSTOPPED (status):
-            raise ExceptionPexpect ('Wait was called for a child process that is stopped. This is not supported. Is some other process attempting job control with our child pid?')
+        elif os.WIFSTOPPED(status):
+            # You can't call wait() on a child process in the stopped state.
+            raise ExceptionPexpect('Called wait() on a stopped child ' +
+                    'process. This is not supported. Is some other ' +
+                    'process attempting job control with our child pid?')
         return self.exitstatus
 
     def isalive(self):
 
-        """This tests if the child process is running or not. This is
+        '''This tests if the child process is running or not. This is
         non-blocking. If the child was terminated then this will read the
         exitstatus or signalstatus of the child. This returns True if the child
         process appears to be running or False if not. It can take literally
-        SECONDS for Solaris to return the right status. """
+        SECONDS for Solaris to return the right status. '''
 
         if self.terminated:
             return False
 
         if self.flag_eof:
-            # This is for Linux, which requires the blocking form of waitpid to get
-            # status of a defunct process. This is super-lame. The flag_eof would have
-            # been set in read_nonblocking(), so this should be safe.
+            # This is for Linux, which requires the blocking form
+            # of waitpid to # get status of a defunct process.
+            # This is super-lame. The flag_eof would have been set
+            # in read_nonblocking(), so this should be safe.
             waitpid_options = 0
         else:
             waitpid_options = os.WNOHANG
 
         try:
             pid, status = os.waitpid(self.pid, waitpid_options)
-        except OSError as e: # No child processes
-            if e.errno == errno.ECHILD:
-                raise ExceptionPexpect ('isalive() encountered condition where "terminated" is 0, but there was no child process. Did someone else call waitpid() on our process?')
+        except OSError:
+            err = sys.exc_info()[1]
+            # No child processes
+            if err.errno == errno.ECHILD:
+                raise ExceptionPexpect('isalive() encountered condition ' +
+                        'where "terminated" is 0, but there was no child ' +
+                        'process. Did someone else call waitpid() ' +
+                        'on our process?')
             else:
-                raise e
+                raise err
 
-        # I have to do this twice for Solaris. I can't even believe that I figured this out...
-        # If waitpid() returns 0 it means that no child process wishes to
-        # report, and the value of status is undefined.
+        # I have to do this twice for Solaris.
+        # I can't even believe that I figured this out...
+        # If waitpid() returns 0 it means that no child process
+        # wishes to report, and the value of status is undefined.
         if pid == 0:
             try:
-                pid, status = os.waitpid(self.pid, waitpid_options) ### os.WNOHANG) # Solaris!
-            except OSError as e: # This should never happen...
-                if e[0] == errno.ECHILD:
-                    raise ExceptionPexpect ('isalive() encountered condition that should never happen. There was no child process. Did someone else call waitpid() on our process?')
+                ### os.WNOHANG) # Solaris!
+                pid, status = os.waitpid(self.pid, waitpid_options)
+            except OSError as e:
+                # This should never happen...
+                if e.errno == errno.ECHILD:
+                    raise ExceptionPexpect('isalive() encountered condition ' +
+                            'that should never happen. There was no child ' +
+                            'process. Did someone else call waitpid() ' +
+                            'on our process?')
                 else:
-                    raise e
+                    raise
 
-            # If pid is still 0 after two calls to waitpid() then
-            # the process really is alive. This seems to work on all platforms, except
-            # for Irix which seems to require a blocking call on waitpid or select, so I let read_nonblocking
-            # take care of this situation (unfortunately, this requires waiting through the timeout).
+            # If pid is still 0 after two calls to waitpid() then the process
+            # really is alive. This seems to work on all platforms, except for
+            # Irix which seems to require a blocking call on waitpid or select,
+            # so I let read_nonblocking take care of this situation
+            # (unfortunately, this requires waiting through the timeout).
             if pid == 0:
                 return True
 
         if pid == 0:
             return True
 
-        if os.WIFEXITED (status):
+        if os.WIFEXITED(status):
             self.status = status
             self.exitstatus = os.WEXITSTATUS(status)
             self.signalstatus = None
             self.terminated = True
-        elif os.WIFSIGNALED (status):
+        elif os.WIFSIGNALED(status):
             self.status = status
             self.exitstatus = None
             self.signalstatus = os.WTERMSIG(status)
             self.terminated = True
-        elif os.WIFSTOPPED (status):
-            raise ExceptionPexpect ('isalive() encountered condition where child process is stopped. This is not supported. Is some other process attempting job control with our child pid?')
+        elif os.WIFSTOPPED(status):
+            raise ExceptionPexpect('isalive() encountered condition ' +
+                    'where child process is stopped. This is not ' +
+                    'supported. Is some other process attempting ' +
+                    'job control with our child pid?')
         return False
 
     def kill(self, sig):
 
-        """This sends the given signal to the child application. In keeping
+        '''This sends the given signal to the child application. In keeping
         with UNIX tradition it has a misleading name. It does not necessarily
-        kill the child unless you send the right signal. """
+        kill the child unless you send the right signal. '''
 
         # Same as os.kill, but the pid is given for you.
         if self.isalive():
             os.kill(self.pid, sig)
 
+    def _pattern_type_err(self, pattern):
+        raise TypeError('got {badtype} ({badobj!r}) as pattern, must be one'
+                        ' of: {goodtypes}, pexpect.EOF, pexpect.TIMEOUT'\
+                        .format(badtype=type(pattern),
+                                badobj=pattern,
+                                goodtypes=', '.join([str(ast)\
+                                    for ast in self.allowed_string_types])
+                                )
+                        )
+
     def compile_pattern_list(self, patterns):
 
-        """This compiles a pattern-string or a list of pattern-strings.
+        '''This compiles a pattern-string or a list of pattern-strings.
         Patterns must be a StringType, EOF, TIMEOUT, SRE_Pattern, or a list of
         those. Patterns may also be None which results in an empty list (you
         might do this if waiting for an EOF or TIMEOUT condition without
@@ -1246,42 +1310,35 b' class spawnb(object):'
                 ...
                 i = self.expect_list(clp, timeout)
                 ...
-        """
+        '''
 
         if patterns is None:
             return []
         if not isinstance(patterns, list):
             patterns = [patterns]
 
-        compile_flags = re.DOTALL # Allow dot to match \n
+        # Allow dot to match \n
+        compile_flags = re.DOTALL
         if self.ignorecase:
             compile_flags = compile_flags | re.IGNORECASE
         compiled_pattern_list = []
-        for p in patterns:
-            if isinstance(p, (bytes, unicode_type)):
-                p = self._cast_buffer_type(p)
+        for idx, p in enumerate(patterns):
+            if isinstance(p, self.allowed_string_types):
+                p = self._coerce_expect_string(p)
                 compiled_pattern_list.append(re.compile(p, compile_flags))
             elif p is EOF:
                 compiled_pattern_list.append(EOF)
             elif p is TIMEOUT:
                 compiled_pattern_list.append(TIMEOUT)
-            elif type(p) is re_type:
-                p = self._prepare_regex_pattern(p)
+            elif isinstance(p, type(re.compile(''))):
                 compiled_pattern_list.append(p)
             else:
-                raise TypeError ('Argument must be one of StringTypes, EOF, TIMEOUT, SRE_Pattern, or a list of those type. %s' % str(type(p)))
-
+                self._pattern_type_err(p)
         return compiled_pattern_list
-    
-    def _prepare_regex_pattern(self, p):
-        "Recompile unicode regexes as bytes regexes. Overridden in subclass."
-        if isinstance(p.pattern, unicode_type):
-            p = re.compile(p.pattern.encode('utf-8'), p.flags &~ re.UNICODE)
-        return p
 
-    def expect(self, pattern, timeout = -1, searchwindowsize=-1):
+    def expect(self, pattern, timeout=-1, searchwindowsize=-1):
 
-        """This seeks through the stream until a pattern is matched. The
+        '''This seeks through the stream until a pattern is matched. The
         pattern is overloaded and may take several types. The pattern can be a
         StringType, EOF, a compiled re, or a list of any of those types.
         Strings will be compiled to re types. This returns the index into the
@@ -1291,21 +1348,21 b' class spawnb(object):'
         list. That will cause expect to match an EOF or TIMEOUT condition
         instead of raising an exception.
 
-        If you pass a list of patterns and more than one matches, the first match
-        in the stream is chosen. If more than one pattern matches at that point,
-        the leftmost in the pattern list is chosen. For example::
+        If you pass a list of patterns and more than one matches, the first
+        match in the stream is chosen. If more than one pattern matches at that
+        point, the leftmost in the pattern list is chosen. For example::
 
             # the input is 'foobar'
-            index = p.expect (['bar', 'foo', 'foobar'])
-            # returns 1 ('foo') even though 'foobar' is a "better" match
+            index = p.expect(['bar', 'foo', 'foobar'])
+            # returns 1('foo') even though 'foobar' is a "better" match
 
         Please note, however, that buffering can affect this behavior, since
         input arrives in unpredictable chunks. For example::
 
             # the input is 'foobar'
-            index = p.expect (['foobar', 'foo'])
-            # returns 0 ('foobar') if all input is available at once,
-            # but returs 1 ('foo') if parts of the final 'bar' arrive late
+            index = p.expect(['foobar', 'foo'])
+            # returns 0('foobar') if all input is available at once,
+            # but returs 1('foo') if parts of the final 'bar' arrive late
 
         After a match is found the instance attributes 'before', 'after' and
         'match' will be set. You can see all the data read before the match in
@@ -1322,7 +1379,7 b' class spawnb(object):'
         exception type. The attribute 'match' will be None. This allows you to
         write code like this::
 
-                index = p.expect (['good', 'bad', pexpect.EOF, pexpect.TIMEOUT])
+                index = p.expect(['good', 'bad', pexpect.EOF, pexpect.TIMEOUT])
                 if index == 0:
                     do_something()
                 elif index == 1:
@@ -1335,7 +1392,7 b' class spawnb(object):'
         instead of code like this::
 
                 try:
-                    index = p.expect (['good', 'bad'])
+                    index = p.expect(['good', 'bad'])
                     if index == 0:
                         do_something()
                     elif index == 1:
@@ -1350,32 +1407,34 b' class spawnb(object):'
         child to finish. For example::
 
                 p = pexpect.spawn('/bin/ls')
-                p.expect (pexpect.EOF)
+                p.expect(pexpect.EOF)
                 print p.before
 
         If you are trying to optimize for speed then see expect_list().
-        """
+        '''
 
         compiled_pattern_list = self.compile_pattern_list(pattern)
-        return self.expect_list(compiled_pattern_list, timeout, searchwindowsize)
+        return self.expect_list(compiled_pattern_list,
+                timeout, searchwindowsize)
 
-    def expect_list(self, pattern_list, timeout = -1, searchwindowsize = -1):
+    def expect_list(self, pattern_list, timeout=-1, searchwindowsize=-1):
 
-        """This takes a list of compiled regular expressions and returns the
+        '''This takes a list of compiled regular expressions and returns the
         index into the pattern_list that matched the child output. The list may
-        also contain EOF or TIMEOUT (which are not compiled regular
+        also contain EOF or TIMEOUT(which are not compiled regular
         expressions). This method is similar to the expect() method except that
         expect_list() does not recompile the pattern list on every call. This
         may help if you are trying to optimize for speed, otherwise just use
         the expect() method.  This is called by expect(). If timeout==-1 then
         the self.timeout value is used. If searchwindowsize==-1 then the
-        self.searchwindowsize value is used. """
+        self.searchwindowsize value is used. '''
 
-        return self.expect_loop(searcher_re(pattern_list), timeout, searchwindowsize)
+        return self.expect_loop(searcher_re(pattern_list),
+                timeout, searchwindowsize)
 
-    def expect_exact(self, pattern_list, timeout = -1, searchwindowsize = -1):
+    def expect_exact(self, pattern_list, timeout=-1, searchwindowsize=-1):
 
-        """This is similar to expect(), but uses plain string matching instead
+        '''This is similar to expect(), but uses plain string matching instead
         of compiled regular expressions in 'pattern_list'. The 'pattern_list'
         may be a string; a list or other sequence of strings; or TIMEOUT and
         EOF.
@@ -1385,19 +1444,34 b' class spawnb(object):'
         search to just the end of the input buffer.
 
         This method is also useful when you don't want to have to worry about
-        escaping regular expression characters that you want to match."""
+        escaping regular expression characters that you want to match.'''
 
-        if isinstance(pattern_list, (bytes, unicode_type)) or pattern_list in (TIMEOUT, EOF):
+        if (isinstance(pattern_list, self.allowed_string_types) or
+                pattern_list in (TIMEOUT, EOF)):
             pattern_list = [pattern_list]
-        return self.expect_loop(searcher_string(pattern_list), timeout, searchwindowsize)
 
-    def expect_loop(self, searcher, timeout = -1, searchwindowsize = -1):
+        def prepare_pattern(pattern):
+            if pattern in (TIMEOUT, EOF):
+                return pattern
+            if isinstance(pattern, self.allowed_string_types):
+                return self._coerce_expect_string(pattern)
+            self._pattern_type_err(pattern)
 
-        """This is the common loop used inside expect. The 'searcher' should be
-        an instance of searcher_re or searcher_string, which describes how and what
-        to search for in the input.
+        try:
+            pattern_list = iter(pattern_list)
+        except TypeError:
+            self._pattern_type_err(pattern_list)
+        pattern_list = [prepare_pattern(p) for p in pattern_list]
+        return self.expect_loop(searcher_string(pattern_list),
+                timeout, searchwindowsize)
+
+    def expect_loop(self, searcher, timeout=-1, searchwindowsize=-1):
 
-        See expect() for other arguments, return value and exceptions. """
+        '''This is the common loop used inside expect. The 'searcher' should be
+        an instance of searcher_re or searcher_string, which describes how and
+        what to search for in the input.
+
+        See expect() for other arguments, return value and exceptions. '''
 
         self.searcher = searcher
 
@@ -1411,27 +1485,29 b' class spawnb(object):'
         try:
             incoming = self.buffer
             freshlen = len(incoming)
-            while True: # Keep reading until exception or return.
+            while True:
+                # Keep reading until exception or return.
                 index = searcher.search(incoming, freshlen, searchwindowsize)
                 if index >= 0:
-                    self.buffer = incoming[searcher.end : ]
-                    self.before = incoming[ : searcher.start]
-                    self.after = incoming[searcher.start : searcher.end]
+                    self.buffer = incoming[searcher.end:]
+                    self.before = incoming[: searcher.start]
+                    self.after = incoming[searcher.start: searcher.end]
                     self.match = searcher.match
                     self.match_index = index
                     return self.match_index
                 # No match at this point
-                if timeout is not None and timeout < 0:
-                    raise TIMEOUT ('Timeout exceeded in expect_any().')
+                if (timeout is not None) and (timeout < 0):
+                    raise TIMEOUT('Timeout exceeded in expect_any().')
                 # Still have time left, so read more data
-                c = self.read_nonblocking (self.maxread, timeout)
+                c = self.read_nonblocking(self.maxread, timeout)
                 freshlen = len(c)
-                time.sleep (0.0001)
+                time.sleep(0.0001)
                 incoming = incoming + c
                 if timeout is not None:
                     timeout = end_time - time.time()
-        except EOF as e:
-            self.buffer = self._empty_buffer
+        except EOF:
+            err = sys.exc_info()[1]
+            self.buffer = self.string_type()
             self.before = incoming
             self.after = EOF
             index = searcher.eof_index
@@ -1442,8 +1518,9 b' class spawnb(object):'
             else:
                 self.match = None
                 self.match_index = None
-                raise EOF (str(e) + '\n' + str(self))
-        except TIMEOUT as e:
+                raise EOF(str(err) + '\n' + str(self))
+        except TIMEOUT:
+            err = sys.exc_info()[1]
             self.buffer = incoming
             self.before = incoming
             self.after = TIMEOUT
@@ -1455,7 +1532,7 b' class spawnb(object):'
             else:
                 self.match = None
                 self.match_index = None
-                raise TIMEOUT (str(e) + '\n' + str(self))
+                raise TIMEOUT(str(err) + '\n' + str(self))
         except:
             self.before = incoming
             self.after = None
@@ -1465,40 +1542,35 b' class spawnb(object):'
 
     def getwinsize(self):
 
-        """This returns the terminal window size of the child tty. The return
-        value is a tuple of (rows, cols). """
+        '''This returns the terminal window size of the child tty. The return
+        value is a tuple of (rows, cols). '''
 
         TIOCGWINSZ = getattr(termios, 'TIOCGWINSZ', 1074295912)
         s = struct.pack('HHHH', 0, 0, 0, 0)
-        x = fcntl.ioctl(self.fileno(), TIOCGWINSZ, s)
+        x = fcntl.ioctl(self.child_fd, TIOCGWINSZ, s)
         return struct.unpack('HHHH', x)[0:2]
 
-    def setwinsize(self, r, c):
+    def setwinsize(self, rows, cols):
 
-        """This sets the terminal window size of the child tty. This will cause
+        '''This sets the terminal window size of the child tty. This will cause
         a SIGWINCH signal to be sent to the child. This does not change the
         physical window size. It changes the size reported to TTY-aware
         applications like vi or curses -- applications that respond to the
-        SIGWINCH signal. """
-
-        # Check for buggy platforms. Some Python versions on some platforms
-        # (notably OSF1 Alpha and RedHat 7.1) truncate the value for
-        # termios.TIOCSWINSZ. It is not clear why this happens.
-        # These platforms don't seem to handle the signed int very well;
-        # yet other platforms like OpenBSD have a large negative value for
-        # TIOCSWINSZ and they don't have a truncate problem.
-        # Newer versions of Linux have totally different values for TIOCSWINSZ.
-        # Note that this fix is a hack.
+        SIGWINCH signal. '''
+
+        # Some very old platforms have a bug that causes the value for
+        # termios.TIOCSWINSZ to be truncated. There was a hack here to work
+        # around this, but it caused problems with newer platforms so has been
+        # removed. For details see https://github.com/pexpect/pexpect/issues/39
         TIOCSWINSZ = getattr(termios, 'TIOCSWINSZ', -2146929561)
-        if TIOCSWINSZ == 2148037735: # L is not required in Python >= 2.2.
-            TIOCSWINSZ = -2146929561 # Same bits, but with sign.
         # Note, assume ws_xpixel and ws_ypixel are zero.
-        s = struct.pack('HHHH', r, c, 0, 0)
+        s = struct.pack('HHHH', rows, cols, 0, 0)
         fcntl.ioctl(self.fileno(), TIOCSWINSZ, s)
 
-    def interact(self, escape_character = b'\x1d', input_filter = None, output_filter = None):
+    def interact(self, escape_character=chr(29),
+            input_filter=None, output_filter=None):
 
-        """This gives control of the child process to the interactive user (the
+        '''This gives control of the child process to the interactive user (the
         human at the keyboard). Keystrokes are sent to the child process, and
         the stdout and stderr output of the child process is printed. This
         simply echos the child stdout and child stderr to the real stdout and
@@ -1523,59 +1595,68 b' class spawnb(object):'
             import pexpect, struct, fcntl, termios, signal, sys
             def sigwinch_passthrough (sig, data):
                 s = struct.pack("HHHH", 0, 0, 0, 0)
-                a = struct.unpack('hhhh', fcntl.ioctl(sys.stdout.fileno(), termios.TIOCGWINSZ , s))
+                a = struct.unpack('hhhh', fcntl.ioctl(sys.stdout.fileno(),
+                    termios.TIOCGWINSZ , s))
                 global p
                 p.setwinsize(a[0],a[1])
-            p = pexpect.spawn('/bin/bash') # Note this is global and used in sigwinch_passthrough.
+            # Note this 'p' global and used in sigwinch_passthrough.
+            p = pexpect.spawn('/bin/bash')
             signal.signal(signal.SIGWINCH, sigwinch_passthrough)
             p.interact()
-        """
+        '''
 
         # Flush the buffer.
-        if PY3: self.stdout.write(_cast_unicode(self.buffer, self.encoding))
-        else:   self.stdout.write(self.buffer)
+        self.write_to_stdout(self.buffer)
         self.stdout.flush()
-        self.buffer = self._empty_buffer
+        self.buffer = self.string_type()
         mode = tty.tcgetattr(self.STDIN_FILENO)
         tty.setraw(self.STDIN_FILENO)
+        if PY3:
+            escape_character = escape_character.encode('latin-1')
         try:
             self.__interact_copy(escape_character, input_filter, output_filter)
         finally:
             tty.tcsetattr(self.STDIN_FILENO, tty.TCSAFLUSH, mode)
 
     def __interact_writen(self, fd, data):
-
-        """This is used by the interact() method.
-        """
+        '''This is used by the interact() method.
+        '''
 
         while data != b'' and self.isalive():
             n = os.write(fd, data)
             data = data[n:]
 
     def __interact_read(self, fd):
-
-        """This is used by the interact() method.
-        """
+        '''This is used by the interact() method.
+        '''
 
         return os.read(fd, 1000)
 
-    def __interact_copy(self, escape_character = None, input_filter = None, output_filter = None):
+    def __interact_copy(self, escape_character=None,
+            input_filter=None, output_filter=None):
 
-        """This is used by the interact() method.
-        """
+        '''This is used by the interact() method.
+        '''
 
         while self.isalive():
-            r,w,e = self.__select([self.child_fd, self.STDIN_FILENO], [], [])
+            r, w, e = self.__select([self.child_fd, self.STDIN_FILENO], [], [])
             if self.child_fd in r:
-                data = self.__interact_read(self.child_fd)
-                if output_filter: data = output_filter(data)
+                try:
+                    data = self.__interact_read(self.child_fd)
+                except OSError as e:
+                    # The subprocess may have closed before we get to reading it
+                    if e.errno != errno.EIO:
+                        raise
+                if output_filter:
+                    data = output_filter(data)
                 if self.logfile is not None:
-                    self.logfile.write (data)
+                    self.logfile.write(data)
                     self.logfile.flush()
                 os.write(self.STDOUT_FILENO, data)
             if self.STDIN_FILENO in r:
                 data = self.__interact_read(self.STDIN_FILENO)
-                if input_filter: data = input_filter(data)
+                if input_filter:
+                    data = input_filter(data)
                 i = data.rfind(escape_character)
                 if i != -1:
                     data = data[:i]
@@ -1583,12 +1664,12 b' class spawnb(object):'
                     break
                 self.__interact_writen(self.child_fd, data)
 
-    def __select (self, iwtd, owtd, ewtd, timeout=None):
+    def __select(self, iwtd, owtd, ewtd, timeout=None):
 
-        """This is a wrapper around select.select() that ignores signals. If
+        '''This is a wrapper around select.select() that ignores signals. If
         select.select raises a select.error exception and errno is an EINTR
         error then it is ignored. Mainly this is used to ignore sigwinch
-        (terminal resize). """
+        (terminal resize). '''
 
         # if select() is interrupted by a signal (errno==EINTR) then
         # we loop back and enter the select() again.
@@ -1596,53 +1677,93 b' class spawnb(object):'
             end_time = time.time() + timeout
         while True:
             try:
-                return select.select (iwtd, owtd, ewtd, timeout)
-            except select.error as e:
-                if e.args[0] == errno.EINTR:
-                    # if we loop back we have to subtract the amount of time we already waited.
+                return select.select(iwtd, owtd, ewtd, timeout)
+            except select.error:
+                err = sys.exc_info()[1]
+                if err.args[0] == errno.EINTR:
+                    # if we loop back we have to subtract the
+                    # amount of time we already waited.
                     if timeout is not None:
                         timeout = end_time - time.time()
                         if timeout < 0:
-                            return ([],[],[])
-                else: # something else caused the select.error, so this really is an exception
+                            return([], [], [])
+                else:
+                    # something else caused the select.error, so
+                    # this actually is an exception.
                     raise
 
-class spawn(spawnb):
-    """This is the main class interface for Pexpect. Use this class to start
-    and control child applications."""
-    
-    _buffer_type = unicode_type
-    def _cast_buffer_type(self, s):
-        return _cast_unicode(s, self.encoding)
-    _empty_buffer = u''
-    _pty_newline = u'\r\n'
-    
-    def __init__(self, command, args=[], timeout=30, maxread=2000, searchwindowsize=None,
-                 logfile=None, cwd=None, env=None, encoding='utf-8'):
-        super(spawn, self).__init__(command, args, timeout=timeout, maxread=maxread,
-                    searchwindowsize=searchwindowsize, logfile=logfile, cwd=cwd, env=env)
-        self.encoding = encoding
-    
-    def _prepare_regex_pattern(self, p):
-        "Recompile bytes regexes as unicode regexes."
-        if isinstance(p.pattern, bytes):
-            p = re.compile(p.pattern.decode(self.encoding), p.flags)
-        return p
-    
-    def read_nonblocking(self, size=1, timeout=-1):
-        return super(spawn, self).read_nonblocking(size=size, timeout=timeout)\
-                                    .decode(self.encoding)
-    
-    read_nonblocking.__doc__ = spawnb.read_nonblocking.__doc__
-        
+##############################################################################
+# The following methods are no longer supported or allowed.
+
+    def setmaxread(self, maxread):
+
+        '''This method is no longer supported or allowed. I don't like getters
+        and setters without a good reason. '''
+
+        raise ExceptionPexpect('This method is no longer supported ' +
+                'or allowed. Just assign a value to the ' +
+                'maxread member variable.')
+
+    def setlog(self, fileobject):
+
+        '''This method is no longer supported or allowed.
+        '''
+
+        raise ExceptionPexpect('This method is no longer supported ' +
+                'or allowed. Just assign a value to the logfile ' +
+                'member variable.')
 
 ##############################################################################
 # End of spawn class
 ##############################################################################
 
-class searcher_string (object):
+class spawnu(spawn):
+    """Works like spawn, but accepts and returns unicode strings.
+
+    Extra parameters:
+
+    :param encoding: The encoding to use for communications (default: 'utf-8')
+    :param errors: How to handle encoding/decoding errors; one of 'strict'
+                   (the default), 'ignore', or 'replace', as described
+                   for :meth:`~bytes.decode` and :meth:`~str.encode`.
+    """
+    if PY3:
+        string_type = str
+        allowed_string_types = (str, )
+        _chr = staticmethod(chr)
+        linesep = os.linesep
+    else:
+        string_type = unicode
+        allowed_string_types = (unicode, )
+        _chr = staticmethod(unichr)
+        linesep = os.linesep.decode('ascii')
+    # This can handle unicode in both Python 2 and 3
+    write_to_stdout = sys.stdout.write
+
+    def __init__(self, *args, **kwargs):
+        self.encoding = kwargs.pop('encoding', 'utf-8')
+        self.errors = kwargs.pop('errors', 'strict')
+        self._decoder = codecs.getincrementaldecoder(self.encoding)(errors=self.errors)
+        super(spawnu, self).__init__(*args, **kwargs)
+
+    @staticmethod
+    def _coerce_expect_string(s):
+        return s
 
-    """This is a plain string search helper for the spawn.expect_any() method.
+    @staticmethod
+    def _coerce_send_string(s):
+        return s
+
+    def _coerce_read_string(self, s):
+        return self._decoder.decode(s, final=False)
+
+    def _send(self, s):
+        return os.write(self.child_fd, s.encode(self.encoding, self.errors))
+
+
+class searcher_string(object):
+
+    '''This is a plain string search helper for the spawn.expect_any() method.
     This helper class is for speed. For more powerful regex patterns
     see the helper class, searcher_re.
 
@@ -1658,12 +1779,12 b' class searcher_string (object):'
         end   - index into the buffer, first byte after match
         match - the matching string itself
 
-    """
+    '''
 
     def __init__(self, strings):
 
-        """This creates an instance of searcher_string. This argument 'strings'
-        may be a list; a sequence of strings; or the EOF or TIMEOUT types. """
+        '''This creates an instance of searcher_string. This argument 'strings'
+        may be a list; a sequence of strings; or the EOF or TIMEOUT types. '''
 
         self.eof_index = -1
         self.timeout_index = -1
@@ -1679,21 +1800,23 b' class searcher_string (object):'
 
     def __str__(self):
 
-        """This returns a human-readable string that represents the state of
-        the object."""
+        '''This returns a human-readable string that represents the state of
+        the object.'''
 
-        ss =  [ (ns[0],'    %d: "%s"' % ns) for ns in self._strings ]
-        ss.append((-1,'searcher_string:'))
+        ss = [(ns[0], '    %d: "%s"' % ns) for ns in self._strings]
+        ss.append((-1, 'searcher_string:'))
         if self.eof_index >= 0:
-            ss.append ((self.eof_index,'    %d: EOF' % self.eof_index))
+            ss.append((self.eof_index, '    %d: EOF' % self.eof_index))
         if self.timeout_index >= 0:
-            ss.append ((self.timeout_index,'    %d: TIMEOUT' % self.timeout_index))
+            ss.append((self.timeout_index,
+                '    %d: TIMEOUT' % self.timeout_index))
         ss.sort()
-        return '\n'.join(a[1] for a in ss)
+        ss = list(zip(*ss))[1]
+        return '\n'.join(ss)
 
     def search(self, buffer, freshlen, searchwindowsize=None):
 
-        """This searches 'buffer' for the first occurence of one of the search
+        '''This searches 'buffer' for the first occurence of one of the search
         strings.  'freshlen' must indicate the number of bytes at the end of
         'buffer' which have not been searched before. It helps to avoid
         searching the same, possibly big, buffer over and over again.
@@ -1701,10 +1824,9 b' class searcher_string (object):'
         See class spawn for the 'searchwindowsize' argument.
 
         If there is a match this returns the index of that string, and sets
-        'start', 'end' and 'match'. Otherwise, this returns -1. """
+        'start', 'end' and 'match'. Otherwise, this returns -1. '''
 
-        absurd_match = len(buffer)
-        first_match = absurd_match
+        first_match = None
 
         # 'freshlen' helps a lot here. Further optimizations could
         # possibly include:
@@ -1722,24 +1844,25 b' class searcher_string (object):'
             if searchwindowsize is None:
                 # the match, if any, can only be in the fresh data,
                 # or at the very end of the old data
-                offset = -(freshlen+len(s))
+                offset = -(freshlen + len(s))
             else:
                 # better obey searchwindowsize
                 offset = -searchwindowsize
             n = buffer.find(s, offset)
-            if n >= 0 and n < first_match:
+            if n >= 0 and (first_match is None or n < first_match):
                 first_match = n
                 best_index, best_match = index, s
-        if first_match == absurd_match:
+        if first_match is None:
             return -1
         self.match = best_match
         self.start = first_match
         self.end = self.start + len(self.match)
         return best_index
 
-class searcher_re (object):
 
-    """This is regular expression string search helper for the
+class searcher_re(object):
+
+    '''This is regular expression string search helper for the
     spawn.expect_any() method. This helper class is for powerful
     pattern matching. For speed, see the helper class, searcher_string.
 
@@ -1755,18 +1878,18 b' class searcher_re (object):'
         end   - index into the buffer, first byte after match
         match - the re.match object returned by a succesful re.search
 
-    """
+    '''
 
     def __init__(self, patterns):
 
-        """This creates an instance that searches for 'patterns' Where
+        '''This creates an instance that searches for 'patterns' Where
         'patterns' may be a list or other sequence of compiled regular
-        expressions, or the EOF or TIMEOUT types."""
+        expressions, or the EOF or TIMEOUT types.'''
 
         self.eof_index = -1
         self.timeout_index = -1
         self._searches = []
-        for n, s in enumerate(patterns):
+        for n, s in zip(list(range(len(patterns))), patterns):
             if s is EOF:
                 self.eof_index = n
                 continue
@@ -1777,83 +1900,93 b' class searcher_re (object):'
 
     def __str__(self):
 
-        """This returns a human-readable string that represents the state of
-        the object."""
+        '''This returns a human-readable string that represents the state of
+        the object.'''
 
-        ss =  [ (n,'    %d: re.compile("%s")' % (n,str(s.pattern))) for n,s in self._searches]
-        ss.append((-1,'searcher_re:'))
+        #ss = [(n, '    %d: re.compile("%s")' %
+        #    (n, repr(s.pattern))) for n, s in self._searches]
+        ss = list()
+        for n, s in self._searches:
+            try:
+                ss.append((n, '    %d: re.compile("%s")' % (n, s.pattern)))
+            except UnicodeEncodeError:
+                # for test cases that display __str__ of searches, dont throw
+                # another exception just because stdout is ascii-only, using
+                # repr()
+                ss.append((n, '    %d: re.compile(%r)' % (n, s.pattern)))
+        ss.append((-1, 'searcher_re:'))
         if self.eof_index >= 0:
-            ss.append ((self.eof_index,'    %d: EOF' % self.eof_index))
+            ss.append((self.eof_index, '    %d: EOF' % self.eof_index))
         if self.timeout_index >= 0:
-            ss.append ((self.timeout_index,'    %d: TIMEOUT' % self.timeout_index))
+            ss.append((self.timeout_index, '    %d: TIMEOUT' %
+                self.timeout_index))
         ss.sort()
-        return '\n'.join(a[1] for a in ss)
+        ss = list(zip(*ss))[1]
+        return '\n'.join(ss)
 
     def search(self, buffer, freshlen, searchwindowsize=None):
 
-        """This searches 'buffer' for the first occurence of one of the regular
+        '''This searches 'buffer' for the first occurence of one of the regular
         expressions. 'freshlen' must indicate the number of bytes at the end of
         'buffer' which have not been searched before.
 
         See class spawn for the 'searchwindowsize' argument.
 
         If there is a match this returns the index of that string, and sets
-        'start', 'end' and 'match'. Otherwise, returns -1."""
+        'start', 'end' and 'match'. Otherwise, returns -1.'''
 
-        absurd_match = len(buffer)
-        first_match = absurd_match
+        first_match = None
         # 'freshlen' doesn't help here -- we cannot predict the
         # length of a match, and the re module provides no help.
         if searchwindowsize is None:
             searchstart = 0
         else:
-            searchstart = max(0, len(buffer)-searchwindowsize)
+            searchstart = max(0, len(buffer) - searchwindowsize)
         for index, s in self._searches:
             match = s.search(buffer, searchstart)
             if match is None:
                 continue
             n = match.start()
-            if n < first_match:
+            if first_match is None or n < first_match:
                 first_match = n
                 the_match = match
                 best_index = index
-        if first_match == absurd_match:
+        if first_match is None:
             return -1
         self.start = first_match
         self.match = the_match
         self.end = self.match.end()
         return best_index
 
-def which (filename):
 
-    """This takes a given filename; tries to find it in the environment path;
+def which(filename):
+
+    '''This takes a given filename; tries to find it in the environment path;
     then checks if it is executable. This returns the full path to the filename
-    if found and executable. Otherwise this returns None."""
+    if found and executable. Otherwise this returns None.'''
 
-    # Special case where filename already contains a path.
+    # Special case where filename contains an explicit path.
     if os.path.dirname(filename) != '':
-        if os.access (filename, os.X_OK):
+        if os.access(filename, os.X_OK):
             return filename
-
     if 'PATH' not in os.environ or os.environ['PATH'] == '':
         p = os.defpath
     else:
         p = os.environ['PATH']
-
     pathlist = p.split(os.pathsep)
-
     for path in pathlist:
-        f = os.path.join(path, filename)
-        if os.access(f, os.X_OK):
-            return f
+        ff = os.path.join(path, filename)
+        if os.access(ff, os.X_OK):
+            return ff
     return None
 
+
 def split_command_line(command_line):
 
-    """This splits a command line into a list of arguments. It splits arguments
+    '''This splits a command line into a list of arguments. It splits arguments
     on spaces, but handles embedded quotes, doublequotes, and escaped
     characters. It's impossible to do this with a regular expression, so I
-    wrote a little state machine to parse the command line. """
+    wrote a little state machine to parse the command line. '''
 
     arg_list = []
     arg = ''
@@ -1863,21 +1996,26 b' def split_command_line(command_line):'
     state_esc = 1
     state_singlequote = 2
     state_doublequote = 3
-    state_whitespace = 4 # The state of consuming whitespace between commands.
+    # The state when consuming whitespace between commands.
+    state_whitespace = 4
     state = state_basic
 
     for c in command_line:
         if state == state_basic or state == state_whitespace:
-            if c == '\\': # Escape the next character
+            if c == '\\':
+                # Escape the next character
                 state = state_esc
-            elif c == r"'": # Handle single quote
+            elif c == r"'":
+                # Handle single quote
                 state = state_singlequote
-            elif c == r'"': # Handle double quote
+            elif c == r'"':
+                # Handle double quote
                 state = state_doublequote
             elif c.isspace():
                 # Add arg to arg_list if we aren't in the middle of whitespace.
                 if state == state_whitespace:
-                    None # Do nothing.
+                    # Do nothing.
+                    None
                 else:
                     arg_list.append(arg)
                     arg = ''