determine encoding of source lines in %debug before colorizing

IPython/core/debugger.py

@@ -1,527 +1,529 b''
 # -*- coding: utf-8 -*-
 """
 Pdb debugger class.
 
 Modified from the standard pdb.Pdb class to avoid including readline, so that
 the command line completion of other programs which include this isn't
 damaged.
 
 In the future, this class will be expanded with improvements over the standard
 pdb.
 
 The code in this file is mainly lifted out of cmd.py in Python 2.2, with minor
 changes. Licensing should therefore be under the standard Python terms.  For
 details on the PSF (Python Software Foundation) standard license, see:
 
 http://www.python.org/2.2.3/license.html"""
 
 #*****************************************************************************
 #
 #       This file is licensed under the PSF license.
 #
 #       Copyright (C) 2001 Python Software Foundation, www.python.org
 #       Copyright (C) 2005-2006 Fernando Perez. <[e-mail]>
 #
 #
 #*****************************************************************************
 from __future__ import print_function
 
 import bdb
 import linecache
 import sys
 
 from IPython.utils import PyColorize
 from IPython.core import ipapi
 from IPython.utils import coloransi, io
 from IPython.core.excolors import exception_colors
 
 # See if we can use pydb.
 has_pydb = False
 prompt = 'ipdb> '
 #We have to check this directly from sys.argv, config struct not yet available
 if '--pydb' in sys.argv:
     try:
         import pydb
         if hasattr(pydb.pydb, "runl") and pydb.version>'1.17':
             # Version 1.17 is broken, and that's what ships with Ubuntu Edgy, so we
             # better protect against it.
             has_pydb = True
     except ImportError:
         print("Pydb (http://bashdb.sourceforge.net/pydb/) does not seem to be available")
 
 if has_pydb:
     from pydb import Pdb as OldPdb
     #print "Using pydb for %run -d and post-mortem" #dbg
     prompt = 'ipydb> '
 else:
     from pdb import Pdb as OldPdb
 
 # Allow the set_trace code to operate outside of an ipython instance, even if
 # it does so with some limitations.  The rest of this support is implemented in
 # the Tracer constructor.
 def BdbQuit_excepthook(et,ev,tb):
     if et==bdb.BdbQuit:
         print('Exiting Debugger.')
     else:
         BdbQuit_excepthook.excepthook_ori(et,ev,tb)
 
 def BdbQuit_IPython_excepthook(self,et,ev,tb,tb_offset=None):
     print('Exiting Debugger.')
 
 
 class Tracer(object):
     """Class for local debugging, similar to pdb.set_trace.
 
     Instances of this class, when called, behave like pdb.set_trace, but
     providing IPython's enhanced capabilities.
 
     This is implemented as a class which must be initialized in your own code
     and not as a standalone function because we need to detect at runtime
     whether IPython is already active or not.  That detection is done in the
     constructor, ensuring that this code plays nicely with a running IPython,
     while functioning acceptably (though with limitations) if outside of it.
     """
 
     def __init__(self,colors=None):
         """Create a local debugger instance.
 
         :Parameters:
 
           - `colors` (None): a string containing the name of the color scheme to
         use, it must be one of IPython's valid color schemes.  If not given, the
         function will default to the current IPython scheme when running inside
         IPython, and to 'NoColor' otherwise.
 
         Usage example:
 
         from IPython.core.debugger import Tracer; debug_here = Tracer()
 
         ... later in your code
         debug_here()  # -> will open up the debugger at that point.
 
         Once the debugger activates, you can use all of its regular commands to
         step through code, set breakpoints, etc.  See the pdb documentation
         from the Python standard library for usage details.
         """
 
         try:
             ip = get_ipython()
         except NameError:
             # Outside of ipython, we set our own exception hook manually
             BdbQuit_excepthook.excepthook_ori = sys.excepthook
             sys.excepthook = BdbQuit_excepthook
             def_colors = 'NoColor'
             try:
                 # Limited tab completion support
                 import readline
                 readline.parse_and_bind('tab: complete')
             except ImportError:
                 pass
         else:
             # In ipython, we use its custom exception handler mechanism
             def_colors = ip.colors
             ip.set_custom_exc((bdb.BdbQuit,), BdbQuit_IPython_excepthook)
 
         if colors is None:
             colors = def_colors
 
         # The stdlib debugger internally uses a modified repr from the `repr`
         # module, that limits the length of printed strings to a hardcoded
         # limit of 30 characters.  That much trimming is too aggressive, let's
         # at least raise that limit to 80 chars, which should be enough for
         # most interactive uses.
         try:
             from repr import aRepr
             aRepr.maxstring = 80
         except:
             # This is only a user-facing convenience, so any error we encounter
             # here can be warned about but can be otherwise ignored.  These
             # printouts will tell us about problems if this API changes 
             import traceback
             traceback.print_exc()
 
         self.debugger = Pdb(colors)
 
     def __call__(self):
         """Starts an interactive debugger at the point where called.
 
         This is similar to the pdb.set_trace() function from the std lib, but
         using IPython's enhanced debugger."""
 
         self.debugger.set_trace(sys._getframe().f_back)
 
 
 def decorate_fn_with_doc(new_fn, old_fn, additional_text=""):
     """Make new_fn have old_fn's doc string. This is particularly useful
     for the do_... commands that hook into the help system.
     Adapted from from a comp.lang.python posting
     by Duncan Booth."""
     def wrapper(*args, **kw):
         return new_fn(*args, **kw)
     if old_fn.__doc__:
         wrapper.__doc__ = old_fn.__doc__ + additional_text
     return wrapper
 
 
 def _file_lines(fname):
     """Return the contents of a named file as a list of lines.
 
     This function never raises an IOError exception: if the file can't be
     read, it simply returns an empty list."""
 
     try:
         outfile = open(fname)
     except IOError:
         return []
     else:
         out = outfile.readlines()
         outfile.close()
         return out
 
 
 class Pdb(OldPdb):
     """Modified Pdb class, does not load readline."""
 
     def __init__(self,color_scheme='NoColor',completekey=None,
                  stdin=None, stdout=None):
 
         # Parent constructor:
         if has_pydb and completekey is None:
             OldPdb.__init__(self,stdin=stdin,stdout=io.stdout)
         else:
             OldPdb.__init__(self,completekey,stdin,stdout)
 
         self.prompt = prompt # The default prompt is '(Pdb)'
 
         # IPython changes...
         self.is_pydb = has_pydb
 
         self.shell = ipapi.get()
 
         if self.is_pydb:
 
             # interactiveshell.py's ipalias seems to want pdb's checkline
             # which located in pydb.fn
             import pydb.fns
             self.checkline = lambda filename, lineno: \
                              pydb.fns.checkline(self, filename, lineno)
 
             self.curframe = None
             self.do_restart = self.new_do_restart
 
             self.old_all_completions = self.shell.Completer.all_completions
             self.shell.Completer.all_completions=self.all_completions
 
             self.do_list = decorate_fn_with_doc(self.list_command_pydb,
                                                 OldPdb.do_list)
             self.do_l     = self.do_list
             self.do_frame = decorate_fn_with_doc(self.new_do_frame,
                                                  OldPdb.do_frame)
 
         self.aliases = {}
 
         # Create color table: we copy the default one from the traceback
         # module and add a few attributes needed for debugging
         self.color_scheme_table = exception_colors()
 
         # shorthands
         C = coloransi.TermColors
         cst = self.color_scheme_table
 
         cst['NoColor'].colors.breakpoint_enabled = C.NoColor
         cst['NoColor'].colors.breakpoint_disabled = C.NoColor
 
         cst['Linux'].colors.breakpoint_enabled = C.LightRed
         cst['Linux'].colors.breakpoint_disabled = C.Red
 
         cst['LightBG'].colors.breakpoint_enabled = C.LightRed
         cst['LightBG'].colors.breakpoint_disabled = C.Red
 
         self.set_colors(color_scheme)
 
         # Add a python parser so we can syntax highlight source while
         # debugging.
         self.parser = PyColorize.Parser()
 
     def set_colors(self, scheme):
         """Shorthand access to the color table scheme selector method."""
         self.color_scheme_table.set_active_scheme(scheme)
 
     def interaction(self, frame, traceback):
         self.shell.set_completer_frame(frame)
         OldPdb.interaction(self, frame, traceback)
 
     def new_do_up(self, arg):
         OldPdb.do_up(self, arg)
         self.shell.set_completer_frame(self.curframe)
     do_u = do_up = decorate_fn_with_doc(new_do_up, OldPdb.do_up)
 
     def new_do_down(self, arg):
         OldPdb.do_down(self, arg)
         self.shell.set_completer_frame(self.curframe)
 
     do_d = do_down = decorate_fn_with_doc(new_do_down, OldPdb.do_down)
 
     def new_do_frame(self, arg):
         OldPdb.do_frame(self, arg)
         self.shell.set_completer_frame(self.curframe)
 
     def new_do_quit(self, arg):
 
         if hasattr(self, 'old_all_completions'):
             self.shell.Completer.all_completions=self.old_all_completions
 
 
         return OldPdb.do_quit(self, arg)
 
     do_q = do_quit = decorate_fn_with_doc(new_do_quit, OldPdb.do_quit)
 
     def new_do_restart(self, arg):
         """Restart command. In the context of ipython this is exactly the same
         thing as 'quit'."""
         self.msg("Restart doesn't make sense here. Using 'quit' instead.")
         return self.do_quit(arg)
 
     def postloop(self):
         self.shell.set_completer_frame(None)
 
     def print_stack_trace(self):
         try:
             for frame_lineno in self.stack:
                 self.print_stack_entry(frame_lineno, context = 5)
         except KeyboardInterrupt:
             pass
 
     def print_stack_entry(self,frame_lineno,prompt_prefix='\n-> ',
                           context = 3):
         #frame, lineno = frame_lineno
         print(self.format_stack_entry(frame_lineno, '', context), file=io.stdout)
 
         # vds: >>
         frame, lineno = frame_lineno
         filename = frame.f_code.co_filename
         self.shell.hooks.synchronize_with_editor(filename, lineno, 0)
         # vds: <<
 
     def format_stack_entry(self, frame_lineno, lprefix=': ', context = 3):
         import linecache, repr
 
         ret = []
 
         Colors = self.color_scheme_table.active_colors
         ColorsNormal = Colors.Normal
         tpl_link = '%s%%s%s' % (Colors.filenameEm, ColorsNormal)
         tpl_call = '%s%%s%s%%s%s' % (Colors.vName, Colors.valEm, ColorsNormal)
         tpl_line = '%%s%s%%s %s%%s' % (Colors.lineno, ColorsNormal)
         tpl_line_em = '%%s%s%%s %s%%s%s' % (Colors.linenoEm, Colors.line,
                                             ColorsNormal)
 
         frame, lineno = frame_lineno
 
         return_value = ''
         if '__return__' in frame.f_locals:
             rv = frame.f_locals['__return__']
             #return_value += '->'
             return_value += repr.repr(rv) + '\n'
         ret.append(return_value)
 
         #s = filename + '(' + `lineno` + ')'
         filename = self.canonic(frame.f_code.co_filename)
         link = tpl_link % filename
 
         if frame.f_code.co_name:
             func = frame.f_code.co_name
         else:
             func = "<lambda>"
 
         call = ''
         if func != '?':
             if '__args__' in frame.f_locals:
                 args = repr.repr(frame.f_locals['__args__'])
             else:
                 args = '()'
             call = tpl_call % (func, args)
 
         # The level info should be generated in the same format pdb uses, to
         # avoid breaking the pdbtrack functionality of python-mode in *emacs.
         if frame is self.curframe:
             ret.append('> ')
         else:
             ret.append('  ')
         ret.append('%s(%s)%s\n' % (link,lineno,call))
 
         start = lineno - 1 - context//2
         lines = linecache.getlines(filename)
+        encoding = io.guess_encoding(lines)
         start = max(start, 0)
         start = min(start, len(lines) - context)
         lines = lines[start : start + context]
 
         for i,line in enumerate(lines):
             show_arrow = (start + 1 + i == lineno)
             linetpl = (frame is self.curframe or show_arrow) \
                       and tpl_line_em \
                       or tpl_line
             ret.append(self.__format_line(linetpl, filename,
-                                          start + 1 + i, line,
+                                          start + 1 + i, line.decode(encoding),
                                           arrow = show_arrow) )
-
         return ''.join(ret)
 
     def __format_line(self, tpl_line, filename, lineno, line, arrow = False):
         bp_mark = ""
         bp_mark_color = ""
 
         scheme = self.color_scheme_table.active_scheme_name
         new_line, err = self.parser.format2(line, 'str', scheme)
         if not err: line = new_line
 
         bp = None
         if lineno in self.get_file_breaks(filename):
             bps = self.get_breaks(filename, lineno)
             bp = bps[-1]
 
         if bp:
             Colors = self.color_scheme_table.active_colors
             bp_mark = str(bp.number)
             bp_mark_color = Colors.breakpoint_enabled
             if not bp.enabled:
                 bp_mark_color = Colors.breakpoint_disabled
 
         numbers_width = 7
         if arrow:
             # This is the line with the error
             pad = numbers_width - len(str(lineno)) - len(bp_mark)
             if pad >= 3:
                 marker = '-'*(pad-3) + '-> '
             elif pad == 2:
                  marker = '> '
             elif pad == 1:
                  marker = '>'
             else:
                  marker = ''
             num = '%s%s' % (marker, str(lineno))
             line = tpl_line % (bp_mark_color + bp_mark, num, line)
         else:
             num = '%*s' % (numbers_width - len(bp_mark), str(lineno))
             line = tpl_line % (bp_mark_color + bp_mark, num, line)
 
         return line
 
     def list_command_pydb(self, arg):
         """List command to use if we have a newer pydb installed"""
         filename, first, last = OldPdb.parse_list_cmd(self, arg)
         if filename is not None:
             self.print_list_lines(filename, first, last)
 
     def print_list_lines(self, filename, first, last):
         """The printing (as opposed to the parsing part of a 'list'
         command."""
         try:
             Colors = self.color_scheme_table.active_colors
             ColorsNormal = Colors.Normal
             tpl_line = '%%s%s%%s %s%%s' % (Colors.lineno, ColorsNormal)
             tpl_line_em = '%%s%s%%s %s%%s%s' % (Colors.linenoEm, Colors.line, ColorsNormal)
             src = []
+            lines = linecache.getlines(filename)
+            encoding = io.guess_encoding(lines)
             for lineno in range(first, last+1):
-                line = linecache.getline(filename, lineno)
+                line = lines[lineno].decode(encoding)
                 if not line:
                     break
 
                 if lineno == self.curframe.f_lineno:
                     line = self.__format_line(tpl_line_em, filename, lineno, line, arrow = True)
                 else:
                     line = self.__format_line(tpl_line, filename, lineno, line, arrow = False)
 
                 src.append(line)
                 self.lineno = lineno
 
             print(''.join(src), file=io.stdout)
 
         except KeyboardInterrupt:
             pass
 
     def do_list(self, arg):
         self.lastcmd = 'list'
         last = None
         if arg:
             try:
                 x = eval(arg, {}, {})
                 if type(x) == type(()):
                     first, last = x
                     first = int(first)
                     last = int(last)
                     if last < first:
                         # Assume it's a count
                         last = first + last
                 else:
                     first = max(1, int(x) - 5)
             except:
                 print('*** Error in argument:', repr(arg))
                 return
         elif self.lineno is None:
             first = max(1, self.curframe.f_lineno - 5)
         else:
             first = self.lineno + 1
         if last is None:
             last = first + 10
         self.print_list_lines(self.curframe.f_code.co_filename, first, last)
 
         # vds: >>
         lineno = first
         filename = self.curframe.f_code.co_filename
         self.shell.hooks.synchronize_with_editor(filename, lineno, 0)
         # vds: <<
 
     do_l = do_list
 
     def do_pdef(self, arg):
         """The debugger interface to magic_pdef"""
         namespaces = [('Locals', self.curframe.f_locals),
                       ('Globals', self.curframe.f_globals)]
         self.shell.find_line_magic('pdef')(arg, namespaces=namespaces)
 
     def do_pdoc(self, arg):
         """The debugger interface to magic_pdoc"""
         namespaces = [('Locals', self.curframe.f_locals),
                       ('Globals', self.curframe.f_globals)]
         self.shell.find_line_magic('pdoc')(arg, namespaces=namespaces)
 
     def do_pinfo(self, arg):
         """The debugger equivalant of ?obj"""
         namespaces = [('Locals', self.curframe.f_locals),
                       ('Globals', self.curframe.f_globals)]
         self.shell.find_line_magic('pinfo')("pinfo %s" % arg,
                                             namespaces=namespaces)
 
     def checkline(self, filename, lineno):
         """Check whether specified line seems to be executable.
 
         Return `lineno` if it is, 0 if not (e.g. a docstring, comment, blank
         line or EOF). Warning: testing is not comprehensive.
         """
         #######################################################################
         # XXX Hack!  Use python-2.5 compatible code for this call, because with
         # all of our changes, we've drifted from the pdb api in 2.6.  For now,
         # changing:
         #
         #line = linecache.getline(filename, lineno, self.curframe.f_globals)
         # to:
         #
         line = linecache.getline(filename, lineno)
         #
         # does the trick.  But in reality, we need to fix this by reconciling
         # our updates with the new Pdb APIs in Python 2.6.
         #
         # End hack.  The rest of this method is copied verbatim from 2.6 pdb.py
         #######################################################################
 
         if not line:
             print('End of file', file=self.stdout)
             return 0
         line = line.strip()
         # Don't allow setting breakpoint at a blank line
         if (not line or (line[0] == '#') or
              (line[:3] == '"""') or line[:3] == "'''"):
             print('*** Blank or comment', file=self.stdout)
             return 0
         return lineno

IPython/utils/io.py

@@ -1,402 +1,409 b''
 # encoding: utf-8
 """
 IO related utilities.
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2011  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 from __future__ import print_function
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 import re
 import os
 import sys
 import tempfile
 from StringIO import StringIO
 
 #-----------------------------------------------------------------------------
 # Code
 #-----------------------------------------------------------------------------
 
 
 class IOStream:
 
     def __init__(self,stream, fallback=None):
         if not hasattr(stream,'write') or not hasattr(stream,'flush'):
             if fallback is not None:
                 stream = fallback
             else:
                 raise ValueError("fallback required, but not specified")
         self.stream = stream
         self._swrite = stream.write
 
         # clone all methods not overridden:
         def clone(meth):
             return not hasattr(self, meth) and not meth.startswith('_')
         for meth in filter(clone, dir(stream)):
             setattr(self, meth, getattr(stream, meth))
 
     def write(self,data):
         try:
             self._swrite(data)
         except:
             try:
                 # print handles some unicode issues which may trip a plain
                 # write() call.  Emulate write() by using an empty end
                 # argument.
                 print(data, end='', file=self.stream)
             except:
                 # if we get here, something is seriously broken.
                 print('ERROR - failed to write data to stream:', self.stream,
                       file=sys.stderr)
 
     def writelines(self, lines):
         if isinstance(lines, basestring):
             lines = [lines]
         for line in lines:
             self.write(line)
 
     # This class used to have a writeln method, but regular files and streams
     # in Python don't have this method. We need to keep this completely
     # compatible so we removed it.
 
     @property
     def closed(self):
         return self.stream.closed
 
     def close(self):
         pass
 
 # setup stdin/stdout/stderr to sys.stdin/sys.stdout/sys.stderr
 devnull = open(os.devnull, 'a')
 stdin = IOStream(sys.stdin, fallback=devnull)
 stdout = IOStream(sys.stdout, fallback=devnull)
 stderr = IOStream(sys.stderr, fallback=devnull)
 
 class IOTerm:
     """ Term holds the file or file-like objects for handling I/O operations.
 
     These are normally just sys.stdin, sys.stdout and sys.stderr but for
     Windows they can can replaced to allow editing the strings before they are
     displayed."""
 
     # In the future, having IPython channel all its I/O operations through
     # this class will make it easier to embed it into other environments which
     # are not a normal terminal (such as a GUI-based shell)
     def __init__(self, stdin=None, stdout=None, stderr=None):
         mymodule = sys.modules[__name__]
         self.stdin  = IOStream(stdin, mymodule.stdin)
         self.stdout = IOStream(stdout, mymodule.stdout)
         self.stderr = IOStream(stderr, mymodule.stderr)
 
 
 class Tee(object):
     """A class to duplicate an output stream to stdout/err.
 
     This works in a manner very similar to the Unix 'tee' command.
 
     When the object is closed or deleted, it closes the original file given to
     it for duplication.
     """
     # Inspired by:
     # http://mail.python.org/pipermail/python-list/2007-May/442737.html
 
     def __init__(self, file_or_name, mode="w", channel='stdout'):
         """Construct a new Tee object.
 
         Parameters
         ----------
         file_or_name : filename or open filehandle (writable)
           File that will be duplicated
 
         mode : optional, valid mode for open().
           If a filename was give, open with this mode.
 
         channel : str, one of ['stdout', 'stderr']
         """
         if channel not in ['stdout', 'stderr']:
             raise ValueError('Invalid channel spec %s' % channel)
 
         if hasattr(file_or_name, 'write') and hasattr(file_or_name, 'seek'):
             self.file = file_or_name
         else:
             self.file = open(file_or_name, mode)
         self.channel = channel
         self.ostream = getattr(sys, channel)
         setattr(sys, channel, self)
         self._closed = False
 
     def close(self):
         """Close the file and restore the channel."""
         self.flush()
         setattr(sys, self.channel, self.ostream)
         self.file.close()
         self._closed = True
 
     def write(self, data):
         """Write data to both channels."""
         self.file.write(data)
         self.ostream.write(data)
         self.ostream.flush()
 
     def flush(self):
         """Flush both channels."""
         self.file.flush()
         self.ostream.flush()
 
     def __del__(self):
         if not self._closed:
             self.close()
 
 
-def source_to_unicode(txt):
-    """Converts string with python source code to unicode
-    """
-    if isinstance(txt, unicode):
-        return txt
+def guess_encoding(lines):
+    """check list of lines for line matching the source code encoding pattern
     
+    Only check first two lines
+    """
     reg = re.compile("#.*coding[:=]\s*([-\w.]+)")
-    for row in txt.split("\n", 2)[:2]: #We only need to check the first two lines
+    for row in lines[:2]: #We only need to check the first two lines
         result = reg.match(row)
         if result:
             coding = result.groups()[0]
             break
     else:
         coding = "ascii"
+    return coding
+
+def source_to_unicode(txt):
+    """Converts string with python source code to unicode
+    """
+    if isinstance(txt, unicode):
+        return txt
+    coding = guess_encoding(txt.split("\n", 2))
     return txt.decode(coding, errors="replace")
     
 
 def file_read(filename):
     """Read a file and close it.  Returns the file source."""
     fobj = open(filename,'r');
     source = fobj.read();
     fobj.close()
     return source
 
 
 def file_readlines(filename):
     """Read a file and close it.  Returns the file source using readlines()."""
     fobj = open(filename,'r');
     lines = fobj.readlines();
     fobj.close()
     return lines
 
 
 def raw_input_multi(header='', ps1='==> ', ps2='..> ',terminate_str = '.'):
     """Take multiple lines of input.
 
     A list with each line of input as a separate element is returned when a
     termination string is entered (defaults to a single '.'). Input can also
     terminate via EOF (^D in Unix, ^Z-RET in Windows).
 
     Lines of input which end in \\ are joined into single entries (and a
     secondary continuation prompt is issued as long as the user terminates
     lines with \\). This allows entering very long strings which are still
     meant to be treated as single entities.
     """
 
     try:
         if header:
             header += '\n'
         lines = [raw_input(header + ps1)]
     except EOFError:
         return []
     terminate = [terminate_str]
     try:
         while lines[-1:] != terminate:
             new_line = raw_input(ps1)
             while new_line.endswith('\\'):
                 new_line = new_line[:-1] + raw_input(ps2)
             lines.append(new_line)
 
         return lines[:-1]  # don't return the termination command
     except EOFError:
         print()
         return lines
 
 
 def raw_input_ext(prompt='',  ps2='... '):
     """Similar to raw_input(), but accepts extended lines if input ends with \\."""
 
     line = raw_input(prompt)
     while line.endswith('\\'):
         line = line[:-1] + raw_input(ps2)
     return line
 
 
 def ask_yes_no(prompt,default=None):
     """Asks a question and returns a boolean (y/n) answer.
 
     If default is given (one of 'y','n'), it is used if the user input is
     empty. Otherwise the question is repeated until an answer is given.
 
     An EOF is treated as the default answer.  If there is no default, an
     exception is raised to prevent infinite loops.
 
     Valid answers are: y/yes/n/no (match is not case sensitive)."""
 
     answers = {'y':True,'n':False,'yes':True,'no':False}
     ans = None
     while ans not in answers.keys():
         try:
             ans = raw_input(prompt+' ').lower()
             if not ans:  # response was an empty string
                 ans = default
         except KeyboardInterrupt:
             pass
         except EOFError:
             if default in answers.keys():
                 ans = default
                 print()
             else:
                 raise
 
     return answers[ans]
 
 
 class NLprinter:
     """Print an arbitrarily nested list, indicating index numbers.
 
     An instance of this class called nlprint is available and callable as a
     function.
 
     nlprint(list,indent=' ',sep=': ') -> prints indenting each level by 'indent'
     and using 'sep' to separate the index from the value. """
 
     def __init__(self):
         self.depth = 0
 
     def __call__(self,lst,pos='',**kw):
         """Prints the nested list numbering levels."""
         kw.setdefault('indent',' ')
         kw.setdefault('sep',': ')
         kw.setdefault('start',0)
         kw.setdefault('stop',len(lst))
         # we need to remove start and stop from kw so they don't propagate
         # into a recursive call for a nested list.
         start = kw['start']; del kw['start']
         stop = kw['stop']; del kw['stop']
         if self.depth == 0 and 'header' in kw.keys():
             print(kw['header'])
 
         for idx in range(start,stop):
             elem = lst[idx]
             newpos = pos + str(idx)
             if type(elem)==type([]):
                 self.depth += 1
                 self.__call__(elem, newpos+",", **kw)
                 self.depth -= 1
             else:
                 print(kw['indent']*self.depth + newpos + kw["sep"] + repr(elem))
 
 nlprint = NLprinter()
 
 
 def temp_pyfile(src, ext='.py'):
     """Make a temporary python file, return filename and filehandle.
 
     Parameters
     ----------
     src : string or list of strings (no need for ending newlines if list)
       Source code to be written to the file.
 
     ext : optional, string
       Extension for the generated file.
 
     Returns
     -------
     (filename, open filehandle)
       It is the caller's responsibility to close the open file and unlink it.
     """
     fname = tempfile.mkstemp(ext)[1]
     f = open(fname,'w')
     f.write(src)
     f.flush()
     return fname, f
 
 
 def raw_print(*args, **kw):
     """Raw print to sys.__stdout__, otherwise identical interface to print()."""
 
     print(*args, sep=kw.get('sep', ' '), end=kw.get('end', '\n'),
           file=sys.__stdout__)
     sys.__stdout__.flush()
 
 
 def raw_print_err(*args, **kw):
     """Raw print to sys.__stderr__, otherwise identical interface to print()."""
 
     print(*args, sep=kw.get('sep', ' '), end=kw.get('end', '\n'),
           file=sys.__stderr__)
     sys.__stderr__.flush()
 
 
 # Short aliases for quick debugging, do NOT use these in production code.
 rprint = raw_print
 rprinte = raw_print_err
 
 
 class CapturedIO(object):
     """Simple object for containing captured stdout/err StringIO objects"""
     
     def __init__(self, stdout, stderr):
         self._stdout = stdout
         self._stderr = stderr
     
     def __str__(self):
         return self.stdout
     
     @property
     def stdout(self):
         if not self._stdout:
             return ''
         return self._stdout.getvalue()
     
     @property
     def stderr(self):
         if not self._stderr:
             return ''
         return self._stderr.getvalue()
     
     def show(self):
         """write my output to sys.stdout/err as appropriate"""
         sys.stdout.write(self.stdout)
         sys.stderr.write(self.stderr)
         sys.stdout.flush()
         sys.stderr.flush()
     
     __call__ = show
 
 
 class capture_output(object):
     """context manager for capturing stdout/err"""
     stdout = True
     stderr = True
     
     def __init__(self, stdout=True, stderr=True):
         self.stdout = stdout
         self.stderr = stderr
     
     def __enter__(self):
         self.sys_stdout = sys.stdout
         self.sys_stderr = sys.stderr
         
         stdout = stderr = False
         if self.stdout:
             stdout = sys.stdout = StringIO()
         if self.stderr:
             stderr = sys.stderr = StringIO()
         
         return CapturedIO(stdout, stderr)
     
     def __exit__(self, exc_type, exc_value, traceback):
         sys.stdout = self.sys_stdout
         sys.stderr = self.sys_stderr