- Modified clock() to return total (user+system) time. Introduced

  clocku/clocks to specifically return user/system times.

IPython/genutils.py

@@ -1,1731 +1,1751 b''
 # -*- coding: utf-8 -*-
 """
 General purpose utilities.
 
 This is a grab-bag of stuff I find useful in most programs I write. Some of
 these things are also convenient when working at the command line.
 
-$Id: genutils.py 1930 2006-11-26 17:22:13Z vivainio $"""
+$Id: genutils.py 2108 2007-02-23 00:31:17Z fperez $"""
 
 #*****************************************************************************
 #       Copyright (C) 2001-2006 Fernando Perez. <[e-mail]>
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #*****************************************************************************
 
 from IPython import Release
 __author__  = '%s <%s>' % Release.authors['Fernando']
 __license__ = Release.license
 
 #****************************************************************************
 # required modules from the Python standard library
 import __main__
 import commands
 import os
 import re
 import shlex
 import shutil
 import sys
 import tempfile
 import time
 import types
 import warnings
 
 # Other IPython utilities
 from IPython.Itpl import Itpl,itpl,printpl
 from IPython import DPyGetOpt
 from path import path
 if os.name == "nt":
     from IPython.winconsole import get_console_size
 
 #****************************************************************************
 # Exceptions
 class Error(Exception):
     """Base class for exceptions in this module."""
     pass
 
 #----------------------------------------------------------------------------
 class IOStream:
     def __init__(self,stream,fallback):
         if not hasattr(stream,'write') or not hasattr(stream,'flush'):
             stream = fallback
         self.stream = stream
         self._swrite = stream.write
         self.flush = stream.flush
 
     def write(self,data):
         try:
             self._swrite(data)
         except:
             try:
                 # print handles some unicode issues which may trip a plain
                 # write() call.  Attempt to emulate write() by using a
                 # trailing comma
                 print >> self.stream, data,
             except:
                 # if we get here, something is seriously broken.
                 print >> sys.stderr, \
                       'ERROR - failed to write data to stream:', self.stream
         
 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,cin=None,cout=None,cerr=None):
         self.cin  = IOStream(cin,sys.stdin)
         self.cout = IOStream(cout,sys.stdout)
         self.cerr = IOStream(cerr,sys.stderr)
         
 # Global variable to be used for all I/O
 Term = IOTerm()
 
 import IPython.rlineimpl as readline
 # Remake Term to use the readline i/o facilities
 if sys.platform == 'win32' and readline.have_readline:
     
     Term = IOTerm(cout=readline._outputfile,cerr=readline._outputfile)
     
 
 #****************************************************************************
 # Generic warning/error printer, used by everything else
 def warn(msg,level=2,exit_val=1):
     """Standard warning printer. Gives formatting consistency.
 
     Output is sent to Term.cerr (sys.stderr by default).
     
     Options:
     
     -level(2): allows finer control:
       0 -> Do nothing, dummy function.
       1 -> Print message.
       2 -> Print 'WARNING:' + message. (Default level).
       3 -> Print 'ERROR:' + message.
       4 -> Print 'FATAL ERROR:' + message and trigger a sys.exit(exit_val).
 
     -exit_val (1): exit value returned by sys.exit() for a level 4
     warning. Ignored for all other levels."""
     
     if level>0:
         header = ['','','WARNING: ','ERROR: ','FATAL ERROR: ']
         print >> Term.cerr, '%s%s' % (header[level],msg)
         if level == 4:
             print >> Term.cerr,'Exiting.\n'
             sys.exit(exit_val)
 
 def info(msg):
     """Equivalent to warn(msg,level=1)."""
 
     warn(msg,level=1)
 
 def error(msg):
     """Equivalent to warn(msg,level=3)."""
 
     warn(msg,level=3)
 
 def fatal(msg,exit_val=1):
     """Equivalent to warn(msg,exit_val=exit_val,level=4)."""
 
     warn(msg,exit_val=exit_val,level=4)
 
 #---------------------------------------------------------------------------
 # Debugging routines
 # 
 def debugx(expr,pre_msg=''):
     """Print the value of an expression from the caller's frame.
     
     Takes an expression, evaluates it in the caller's frame and prints both
     the given expression and the resulting value (as well as a debug mark
     indicating the name of the calling function.  The input must be of a form
     suitable for eval().
 
     An optional message can be passed, which will be prepended to the printed
     expr->value pair."""
     
     cf = sys._getframe(1)
     print '[DBG:%s] %s%s -> %r' % (cf.f_code.co_name,pre_msg,expr,
                                    eval(expr,cf.f_globals,cf.f_locals))
 
 # deactivate it by uncommenting the following line, which makes it a no-op
 #def debugx(expr,pre_msg=''): pass
 
 #----------------------------------------------------------------------------
 StringTypes = types.StringTypes
 
 # Basic timing functionality
 
 # If possible (Unix), use the resource module instead of time.clock()
 try:
     import resource
-    def clock():
-        """clock() -> floating point number
+    def clocku():
+        """clocku() -> floating point number
 
-        Return the CPU time in seconds (user time only, system time is
-        ignored) since the start of the process.  This is done via a call to
-        resource.getrusage, so it avoids the wraparound problems in
-        time.clock()."""
+        Return the *USER* CPU time in seconds since the start of the process.
+        This is done via a call to resource.getrusage, so it avoids the
+        wraparound problems in time.clock()."""
         
         return resource.getrusage(resource.RUSAGE_SELF)[0]
     
+    def clocks():
+        """clocks() -> floating point number
+
+        Return the *SYSTEM* CPU time in seconds since the start of the process.
+        This is done via a call to resource.getrusage, so it avoids the
+        wraparound problems in time.clock()."""
+        
+        return resource.getrusage(resource.RUSAGE_SELF)[1]
+    
+    def clock():
+        """clock() -> floating point number
+
+        Return the *TOTAL USER+SYSTEM* CPU time in seconds since the start of
+        the process.  This is done via a call to resource.getrusage, so it
+        avoids the wraparound problems in time.clock()."""
+
+        u,s = resource.getrusage(resource.RUSAGE_SELF)[:2] 
+        return u+s
+    
     def clock2():
         """clock2() -> (t_user,t_system)
 
         Similar to clock(), but return a tuple of user/system times."""
         return resource.getrusage(resource.RUSAGE_SELF)[:2]
 
 except ImportError:
-    clock = time.clock
+    # There is no distinction of user/system time under windows, so we just use
+    # time.clock() for everything...
+    clocku = clocks = clock = time.clock
     def clock2():
         """Under windows, system CPU time can't be measured.
 
         This just returns clock() and zero."""
         return time.clock(),0.0
 
 def timings_out(reps,func,*args,**kw):
     """timings_out(reps,func,*args,**kw) -> (t_total,t_per_call,output)
 
     Execute a function reps times, return a tuple with the elapsed total
     CPU time in seconds, the time per call and the function's output.
 
     Under Unix, the return value is the sum of user+system time consumed by
     the process, computed via the resource module.  This prevents problems
     related to the wraparound effect which the time.clock() function has.
     
     Under Windows the return value is in wall clock seconds. See the
     documentation for the time module for more details."""
 
     reps = int(reps)
     assert reps >=1, 'reps must be >= 1'
     if reps==1:
         start = clock()
         out = func(*args,**kw)
         tot_time = clock()-start
     else:
         rng = xrange(reps-1) # the last time is executed separately to store output
         start = clock()
         for dummy in rng: func(*args,**kw)
         out = func(*args,**kw)  # one last time
         tot_time = clock()-start
     av_time = tot_time / reps
     return tot_time,av_time,out
 
 def timings(reps,func,*args,**kw):
     """timings(reps,func,*args,**kw) -> (t_total,t_per_call)
 
     Execute a function reps times, return a tuple with the elapsed total CPU
     time in seconds and the time per call. These are just the first two values
     in timings_out()."""
 
     return timings_out(reps,func,*args,**kw)[0:2]
 
 def timing(func,*args,**kw):
     """timing(func,*args,**kw) -> t_total
 
     Execute a function once, return the elapsed total CPU time in
     seconds. This is just the first value in timings_out()."""
 
     return timings_out(1,func,*args,**kw)[0]
 
 #****************************************************************************
 # file and system
 
 def arg_split(s,posix=False):
     """Split a command line's arguments in a shell-like manner.
 
     This is a modified version of the standard library's shlex.split()
     function, but with a default of posix=False for splitting, so that quotes
     in inputs are respected."""
     
     lex = shlex.shlex(s, posix=posix)
     lex.whitespace_split = True
     return list(lex)
 
 def system(cmd,verbose=0,debug=0,header=''):
     """Execute a system command, return its exit status.
 
     Options:
 
     - verbose (0): print the command to be executed.
     
     - debug (0): only print, do not actually execute.
 
     - header (''): Header to print on screen prior to the executed command (it
     is only prepended to the command, no newlines are added).
 
     Note: a stateful version of this function is available through the
     SystemExec class."""
 
     stat = 0
     if verbose or debug: print header+cmd
     sys.stdout.flush()
     if not debug: stat = os.system(cmd)
     return stat
 
 # This function is used by ipython in a lot of places to make system calls.
 # We need it to be slightly different under win32, due to the vagaries of
 # 'network shares'.  A win32 override is below.
 
 def shell(cmd,verbose=0,debug=0,header=''):
     """Execute a command in the system shell, always return None.
 
     Options:
 
     - verbose (0): print the command to be executed.
     
     - debug (0): only print, do not actually execute.
 
     - header (''): Header to print on screen prior to the executed command (it
     is only prepended to the command, no newlines are added).
 
     Note: this is similar to genutils.system(), but it returns None so it can
     be conveniently used in interactive loops without getting the return value
     (typically 0) printed many times."""
 
     stat = 0
     if verbose or debug: print header+cmd
     # flush stdout so we don't mangle python's buffering
     sys.stdout.flush()
     if not debug:
         os.system(cmd)
 
 # override shell() for win32 to deal with network shares
 if os.name in ('nt','dos'):
 
     shell_ori = shell
 
     def shell(cmd,verbose=0,debug=0,header=''):
         if os.getcwd().startswith(r"\\"):
             path = os.getcwd()
             # change to c drive (cannot be on UNC-share when issuing os.system,
             # as cmd.exe cannot handle UNC addresses)
             os.chdir("c:")
             # issue pushd to the UNC-share and then run the command
             try:
                 shell_ori('"pushd %s&&"'%path+cmd,verbose,debug,header)
             finally:
                 os.chdir(path)
         else:
             shell_ori(cmd,verbose,debug,header)
 
     shell.__doc__ = shell_ori.__doc__
 
 def getoutput(cmd,verbose=0,debug=0,header='',split=0):
     """Dummy substitute for perl's backquotes.
 
     Executes a command and returns the output.
 
     Accepts the same arguments as system(), plus:
 
     - split(0): if true, the output is returned as a list split on newlines.
 
     Note: a stateful version of this function is available through the
     SystemExec class.
     
     This is pretty much deprecated and rarely used, 
     genutils.getoutputerror may be what you need.
     
     """
 
     if verbose or debug: print header+cmd
     if not debug:
         output = os.popen(cmd).read()
         # stipping last \n is here for backwards compat.
         if output.endswith('\n'):
             output = output[:-1]
         if split:
             return output.split('\n')
         else:
             return output
 
 def getoutputerror(cmd,verbose=0,debug=0,header='',split=0):
     """Return (standard output,standard error) of executing cmd in a shell.
 
     Accepts the same arguments as system(), plus:
 
     - split(0): if true, each of stdout/err is returned as a list split on
     newlines.
 
     Note: a stateful version of this function is available through the
     SystemExec class."""
 
     if verbose or debug: print header+cmd
     if not cmd:
         if split:
             return [],[]
         else:
             return '',''
     if not debug:
         pin,pout,perr = os.popen3(cmd)
         tout = pout.read().rstrip()
         terr = perr.read().rstrip()
         pin.close()
         pout.close()
         perr.close()
         if split:
             return tout.split('\n'),terr.split('\n')
         else:
             return tout,terr
 
 # for compatibility with older naming conventions
 xsys = system
 bq = getoutput
 
 class SystemExec:
     """Access the system and getoutput functions through a stateful interface.
 
     Note: here we refer to the system and getoutput functions from this
     library, not the ones from the standard python library.
     
     This class offers the system and getoutput functions as methods, but the
     verbose, debug and header parameters can be set for the instance (at
     creation time or later) so that they don't need to be specified on each
     call.
 
     For efficiency reasons, there's no way to override the parameters on a
     per-call basis other than by setting instance attributes. If you need
     local overrides, it's best to directly call system() or getoutput().
 
     The following names are provided as alternate options:
      - xsys: alias to system
      - bq: alias to getoutput
 
     An instance can then be created as:
      >>> sysexec = SystemExec(verbose=1,debug=0,header='Calling: ')
 
     And used as:
      >>> sysexec.xsys('pwd')
      >>> dirlist = sysexec.bq('ls -l')
     """
     
     def __init__(self,verbose=0,debug=0,header='',split=0):
         """Specify the instance's values for verbose, debug and header."""
         setattr_list(self,'verbose debug header split')
 
     def system(self,cmd):
         """Stateful interface to system(), with the same keyword parameters."""
 
         system(cmd,self.verbose,self.debug,self.header)
 
     def shell(self,cmd):
         """Stateful interface to shell(), with the same keyword parameters."""
 
         shell(cmd,self.verbose,self.debug,self.header)
 
     xsys = system  # alias
 
     def getoutput(self,cmd):
         """Stateful interface to getoutput()."""
 
         return getoutput(cmd,self.verbose,self.debug,self.header,self.split)
 
     def getoutputerror(self,cmd):
         """Stateful interface to getoutputerror()."""
 
         return getoutputerror(cmd,self.verbose,self.debug,self.header,self.split)
 
     bq = getoutput  # alias
 
 #-----------------------------------------------------------------------------
 def mutex_opts(dict,ex_op):
     """Check for presence of mutually exclusive keys in a dict.
 
     Call: mutex_opts(dict,[[op1a,op1b],[op2a,op2b]...]"""
     for op1,op2 in ex_op:
         if op1 in dict and op2 in dict:
             raise ValueError,'\n*** ERROR in Arguments *** '\
                   'Options '+op1+' and '+op2+' are mutually exclusive.'
 
 #-----------------------------------------------------------------------------
 def get_py_filename(name):
     """Return a valid python filename in the current directory.
 
     If the given name is not a file, it adds '.py' and searches again.
     Raises IOError with an informative message if the file isn't found."""
 
     name = os.path.expanduser(name)
     if not os.path.isfile(name) and not name.endswith('.py'):
         name += '.py'
     if os.path.isfile(name):
         return name
     else:
         raise IOError,'File `%s` not found.' % name
 
 #-----------------------------------------------------------------------------
 def filefind(fname,alt_dirs = None):
     """Return the given filename either in the current directory, if it
     exists, or in a specified list of directories.
 
     ~ expansion is done on all file and directory names.
 
     Upon an unsuccessful search, raise an IOError exception."""
 
     if alt_dirs is None:
         try:
             alt_dirs = get_home_dir()
         except HomeDirError:
             alt_dirs = os.getcwd()
     search = [fname] + list_strings(alt_dirs)
     search = map(os.path.expanduser,search)
     #print 'search list for',fname,'list:',search  # dbg
     fname = search[0]
     if os.path.isfile(fname):
         return fname
     for direc in search[1:]:
         testname = os.path.join(direc,fname)
         #print 'testname',testname  # dbg
         if os.path.isfile(testname):
             return testname
     raise IOError,'File' + `fname` + \
           ' not found in current or supplied directories:' + `alt_dirs`
 
 #----------------------------------------------------------------------------
 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 target_outdated(target,deps):
     """Determine whether a target is out of date.
 
     target_outdated(target,deps) -> 1/0
 
     deps: list of filenames which MUST exist.
     target: single filename which may or may not exist.
 
     If target doesn't exist or is older than any file listed in deps, return
     true, otherwise return false.
     """
     try:
         target_time = os.path.getmtime(target)
     except os.error:
         return 1
     for dep in deps:
         dep_time = os.path.getmtime(dep)
         if dep_time > target_time:
             #print "For target",target,"Dep failed:",dep # dbg
             #print "times (dep,tar):",dep_time,target_time # dbg
             return 1
     return 0
 
 #-----------------------------------------------------------------------------
 def target_update(target,deps,cmd):
     """Update a target with a given command given a list of dependencies.
 
     target_update(target,deps,cmd) -> runs cmd if target is outdated.
 
     This is just a wrapper around target_outdated() which calls the given
     command if target is outdated."""
 
     if target_outdated(target,deps):
         xsys(cmd)
 
 #----------------------------------------------------------------------------
 def unquote_ends(istr):
     """Remove a single pair of quotes from the endpoints of a string."""
 
     if not istr:
         return istr
     if (istr[0]=="'" and istr[-1]=="'") or \
        (istr[0]=='"' and istr[-1]=='"'):
         return istr[1:-1]
     else:
         return istr
 
 #----------------------------------------------------------------------------
 def process_cmdline(argv,names=[],defaults={},usage=''):
     """ Process command-line options and arguments.
 
     Arguments:
 
     - argv: list of arguments, typically sys.argv.
     
     - names: list of option names. See DPyGetOpt docs for details on options
     syntax.
 
     - defaults: dict of default values.
 
     - usage: optional usage notice to print if a wrong argument is passed.
 
     Return a dict of options and a list of free arguments."""
 
     getopt = DPyGetOpt.DPyGetOpt()
     getopt.setIgnoreCase(0)
     getopt.parseConfiguration(names)
 
     try:
         getopt.processArguments(argv)
     except:
         print usage
         warn(`sys.exc_value`,level=4)
 
     defaults.update(getopt.optionValues)
     args = getopt.freeValues
     
     return defaults,args
 
 #----------------------------------------------------------------------------
 def optstr2types(ostr):
     """Convert a string of option names to a dict of type mappings.
 
     optstr2types(str) -> {None:'string_opts',int:'int_opts',float:'float_opts'}
 
     This is used to get the types of all the options in a string formatted
     with the conventions of DPyGetOpt. The 'type' None is used for options
     which are strings (they need no further conversion). This function's main
     use is to get a typemap for use with read_dict().
     """
 
     typeconv = {None:'',int:'',float:''}
     typemap = {'s':None,'i':int,'f':float}
     opt_re = re.compile(r'([\w]*)([^:=]*:?=?)([sif]?)')
 
     for w in ostr.split():
         oname,alias,otype = opt_re.match(w).groups()
         if otype == '' or alias == '!':   # simple switches are integers too
             otype = 'i'
         typeconv[typemap[otype]] += oname + ' '
     return typeconv
 
 #----------------------------------------------------------------------------
 def read_dict(filename,type_conv=None,**opt):
 
     """Read a dictionary of key=value pairs from an input file, optionally
     performing conversions on the resulting values.
 
     read_dict(filename,type_conv,**opt) -> dict
 
     Only one value per line is accepted, the format should be
      # optional comments are ignored
      key value\n
 
     Args:
 
       - type_conv: A dictionary specifying which keys need to be converted to
       which types. By default all keys are read as strings. This dictionary
       should have as its keys valid conversion functions for strings
       (int,long,float,complex, or your own).  The value for each key
       (converter) should be a whitespace separated string containing the names
       of all the entries in the file to be converted using that function. For
       keys to be left alone, use None as the conversion function (only needed
       with purge=1, see below).
 
       - opt: dictionary with extra options as below (default in parens)
 
         purge(0): if set to 1, all keys *not* listed in type_conv are purged out
         of the dictionary to be returned. If purge is going to be used, the
         set of keys to be left as strings also has to be explicitly specified
         using the (non-existent) conversion function None.
 
         fs(None): field separator. This is the key/value separator to be used
         when parsing the file. The None default means any whitespace [behavior
         of string.split()].
 
         strip(0): if 1, strip string values of leading/trailinig whitespace.
 
         warn(1): warning level if requested keys are not found in file.
           - 0: silently ignore.
           - 1: inform but proceed.
           - 2: raise KeyError exception.
 
         no_empty(0): if 1, remove keys with whitespace strings as a value.
 
         unique([]): list of keys (or space separated string) which can't be
         repeated. If one such key is found in the file, each new instance
         overwrites the previous one. For keys not listed here, the behavior is
         to make a list of all appearances.
 
     Example:
     If the input file test.ini has:
       i 3
       x 4.5
       y 5.5
       s hi ho
     Then:
 
     >>> type_conv={int:'i',float:'x',None:'s'}
     >>> read_dict('test.ini')
     {'i': '3', 's': 'hi ho', 'x': '4.5', 'y': '5.5'}
     >>> read_dict('test.ini',type_conv)
     {'i': 3, 's': 'hi ho', 'x': 4.5, 'y': '5.5'}
     >>> read_dict('test.ini',type_conv,purge=1)
     {'i': 3, 's': 'hi ho', 'x': 4.5}
     """
 
     # starting config
     opt.setdefault('purge',0)
     opt.setdefault('fs',None)  # field sep defaults to any whitespace
     opt.setdefault('strip',0)
     opt.setdefault('warn',1)
     opt.setdefault('no_empty',0)
     opt.setdefault('unique','')
     if type(opt['unique']) in StringTypes:
         unique_keys = qw(opt['unique'])
     elif type(opt['unique']) in (types.TupleType,types.ListType):
         unique_keys = opt['unique']
     else:
         raise ValueError, 'Unique keys must be given as a string, List or Tuple'
 
     dict = {}
     # first read in table of values as strings
     file = open(filename,'r')
     for line in file.readlines():
         line = line.strip()
         if len(line) and line[0]=='#': continue
         if len(line)>0:
             lsplit = line.split(opt['fs'],1)
             try:
                 key,val = lsplit
             except ValueError:
                 key,val = lsplit[0],''
             key = key.strip()
             if opt['strip']: val = val.strip()
             if val == "''" or val == '""': val = ''
             if opt['no_empty'] and (val=='' or val.isspace()):
                 continue
             # if a key is found more than once in the file, build a list
             # unless it's in the 'unique' list. In that case, last found in file
             # takes precedence. User beware.
             try:
                 if dict[key] and key in unique_keys:
                     dict[key] = val
                 elif type(dict[key]) is types.ListType:
                     dict[key].append(val)
                 else:
                     dict[key] = [dict[key],val]
             except KeyError:
                 dict[key] = val
     # purge if requested
     if opt['purge']:
         accepted_keys = qwflat(type_conv.values())
         for key in dict.keys():
             if key in accepted_keys: continue
             del(dict[key])
     # now convert if requested
     if type_conv==None: return dict
     conversions = type_conv.keys()
     try: conversions.remove(None)
     except: pass
     for convert in conversions:
         for val in qw(type_conv[convert]):
             try:
                 dict[val] = convert(dict[val])
             except KeyError,e:
                 if opt['warn'] == 0:
                     pass
                 elif opt['warn'] == 1:
                     print >>sys.stderr, 'Warning: key',val,\
                           'not found in file',filename
                 elif opt['warn'] == 2:
                     raise KeyError,e
                 else:
                     raise ValueError,'Warning level must be 0,1 or 2'
 
     return dict
 
 #----------------------------------------------------------------------------
 def flag_calls(func):
     """Wrap a function to detect and flag when it gets called.
 
     This is a decorator which takes a function and wraps it in a function with
     a 'called' attribute. wrapper.called is initialized to False.
 
     The wrapper.called attribute is set to False right before each call to the
     wrapped function, so if the call fails it remains False.  After the call
     completes, wrapper.called is set to True and the output is returned.
 
     Testing for truth in wrapper.called allows you to determine if a call to
     func() was attempted and succeeded."""
     
     def wrapper(*args,**kw):
         wrapper.called = False
         out = func(*args,**kw)
         wrapper.called = True
         return out
 
     wrapper.called = False
     wrapper.__doc__ = func.__doc__
     return wrapper
 
 #----------------------------------------------------------------------------
 class HomeDirError(Error):
     pass
 
 def get_home_dir():
     """Return the closest possible equivalent to a 'home' directory.
 
     We first try $HOME.  Absent that, on NT it's $HOMEDRIVE\$HOMEPATH.
 
     Currently only Posix and NT are implemented, a HomeDirError exception is
     raised for all other OSes. """
 
     isdir = os.path.isdir
     env = os.environ
     try:
         homedir = env['HOME']
         if not isdir(homedir):
             # in case a user stuck some string which does NOT resolve to a
             # valid path, it's as good as if we hadn't foud it
             raise KeyError
         return homedir
     except KeyError:
         if os.name == 'posix':
             raise HomeDirError,'undefined $HOME, IPython can not proceed.'
         elif os.name == 'nt':
             # For some strange reason, win9x returns 'nt' for os.name.
             try:
                 homedir = os.path.join(env['HOMEDRIVE'],env['HOMEPATH'])
                 if not isdir(homedir):
                     homedir = os.path.join(env['USERPROFILE'])
                     if not isdir(homedir):
                         raise HomeDirError
                 return homedir
             except:
                 try:
                     # Use the registry to get the 'My Documents' folder.
                     import _winreg as wreg
                     key = wreg.OpenKey(wreg.HKEY_CURRENT_USER,
                                        "Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders")
                     homedir = wreg.QueryValueEx(key,'Personal')[0]
                     key.Close()
                     if not isdir(homedir):
                         e = ('Invalid "Personal" folder registry key '
                              'typically "My Documents".\n'
                              'Value: %s\n'
                              'This is not a valid directory on your system.' %
                              homedir)
                         raise HomeDirError(e)
                     return homedir
                 except HomeDirError:
                     raise
                 except:
                     return 'C:\\'
         elif os.name == 'dos':
             # Desperate, may do absurd things in classic MacOS. May work under DOS.
             return 'C:\\'
         else:
             raise HomeDirError,'support for your operating system not implemented.'
 
 #****************************************************************************
 # strings and text
 
 class LSString(str):
     """String derivative with a special access attributes.
 
     These are normal strings, but with the special attributes:
 
         .l (or .list) : value as list (split on newlines).
         .n (or .nlstr): original value (the string itself).
         .s (or .spstr): value as whitespace-separated string.
         
     Any values which require transformations are computed only once and
     cached.
 
     Such strings are very useful to efficiently interact with the shell, which
     typically only understands whitespace-separated options for commands."""
 
     def get_list(self):
         try:
             return self.__list
         except AttributeError:
             self.__list = self.split('\n')
             return self.__list
 
     l = list = property(get_list)
 
     def get_spstr(self):
         try:
             return self.__spstr
         except AttributeError:
             self.__spstr = self.replace('\n',' ')
             return self.__spstr
 
     s = spstr = property(get_spstr)
 
     def get_nlstr(self):
         return self
 
     n = nlstr = property(get_nlstr)
 
     def get_paths(self):
         try:
             return self.__paths
         except AttributeError:
             self.__paths = [path(p) for p in self.split('\n') if os.path.exists(p)]
             return self.__paths
     
     p = paths = property(get_paths)
 
 
 #----------------------------------------------------------------------------
 class SList(list):
     """List derivative with a special access attributes.
 
     These are normal lists, but with the special attributes:
 
         .l (or .list) : value as list (the list itself).
         .n (or .nlstr): value as a string, joined on newlines.
         .s (or .spstr): value as a string, joined on spaces.
 
     Any values which require transformations are computed only once and
     cached."""
 
     def get_list(self):
         return self
 
     l = list = property(get_list)
 
     def get_spstr(self):
         try:
             return self.__spstr
         except AttributeError:
             self.__spstr = ' '.join(self)
             return self.__spstr
 
     s = spstr = property(get_spstr)
 
     def get_nlstr(self):
         try:
             return self.__nlstr
         except AttributeError:
             self.__nlstr = '\n'.join(self)
             return self.__nlstr
 
     n = nlstr = property(get_nlstr)
     
     def get_paths(self):
         try:
             return self.__paths
         except AttributeError:
             self.__paths = [path(p) for p in self if os.path.exists(p)]
             return self.__paths
     
     p = paths = property(get_paths)
 
 #----------------------------------------------------------------------------
 def esc_quotes(strng):
     """Return the input string with single and double quotes escaped out"""
 
     return strng.replace('"','\\"').replace("'","\\'")
 
 #----------------------------------------------------------------------------
 def make_quoted_expr(s):
     """Return string s in appropriate quotes, using raw string if possible.
     
     Effectively this turns string: cd \ao\ao\
     to: r"cd \ao\ao\_"[:-1]
     
     Note the use of raw string and padding at the end to allow trailing backslash.
     
     """
     
     tail = ''
     tailpadding = ''
     raw  = ''
     if "\\" in s:
         raw = 'r'
         if s.endswith('\\'):
             tail = '[:-1]'
             tailpadding = '_'
     if '"' not in s:
         quote = '"'
     elif "'" not in s:
         quote = "'"
     elif '"""' not in s and not s.endswith('"'):
         quote = '"""'
     elif "'''" not in s and not s.endswith("'"):
         quote = "'''"
     else:
         # give up, backslash-escaped string will do
         return '"%s"' % esc_quotes(s)
     res = itpl("$raw$quote$s$tailpadding$quote$tail")
     return res
 
 
 #----------------------------------------------------------------------------
 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 an integer 1/0 (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]
 
 #----------------------------------------------------------------------------
 def marquee(txt='',width=78,mark='*'):
     """Return the input string centered in a 'marquee'."""
     if not txt:
         return (mark*width)[:width]
     nmark = (width-len(txt)-2)/len(mark)/2
     if nmark < 0: nmark =0
     marks = mark*nmark
     return '%s %s %s' % (marks,txt,marks)
 
 #----------------------------------------------------------------------------
 class EvalDict:
     """
     Emulate a dict which evaluates its contents in the caller's frame.
 
     Usage:
     >>>number = 19
     >>>text = "python"
     >>>print "%(text.capitalize())s %(number/9.0).1f rules!" % EvalDict()
     """
 
     # This version is due to [e-mail] on c.l.py, and is basically a
     # modified (shorter) version of:
     # http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66018 by
     # Skip Montanaro ([e-mail]).
 
     def __getitem__(self, name):
         frame = sys._getframe(1)
         return eval(name, frame.f_globals, frame.f_locals)
 
 EvalString = EvalDict  # for backwards compatibility
 #----------------------------------------------------------------------------
 def qw(words,flat=0,sep=None,maxsplit=-1):
     """Similar to Perl's qw() operator, but with some more options.
 
     qw(words,flat=0,sep=' ',maxsplit=-1) -> words.split(sep,maxsplit)
 
     words can also be a list itself, and with flat=1, the output will be
     recursively flattened. Examples:
 
     >>> qw('1 2')
     ['1', '2']
     >>> qw(['a b','1 2',['m n','p q']])
     [['a', 'b'], ['1', '2'], [['m', 'n'], ['p', 'q']]]
     >>> qw(['a b','1 2',['m n','p q']],flat=1)
     ['a', 'b', '1', '2', 'm', 'n', 'p', 'q']    """
 
     if type(words) in StringTypes:
         return [word.strip() for word in words.split(sep,maxsplit)
                 if word and not word.isspace() ]
     if flat:
         return flatten(map(qw,words,[1]*len(words)))
     return map(qw,words)
 
 #----------------------------------------------------------------------------
 def qwflat(words,sep=None,maxsplit=-1):
     """Calls qw(words) in flat mode. It's just a convenient shorthand."""
     return qw(words,1,sep,maxsplit)
 
 #----------------------------------------------------------------------------
 def qw_lol(indata):
     """qw_lol('a b') -> [['a','b']],
     otherwise it's just a call to qw().
 
     We need this to make sure the modules_some keys *always* end up as a
     list of lists."""
 
     if type(indata) in StringTypes:
         return [qw(indata)]
     else:
         return qw(indata)
 
 #-----------------------------------------------------------------------------
 def list_strings(arg):
     """Always return a list of strings, given a string or list of strings
     as input."""
 
     if type(arg) in StringTypes: return [arg]
     else: return arg
 
 #----------------------------------------------------------------------------
 def grep(pat,list,case=1):
     """Simple minded grep-like function.
     grep(pat,list) returns occurrences of pat in list, None on failure.
 
     It only does simple string matching, with no support for regexps. Use the
     option case=0 for case-insensitive matching."""
 
     # This is pretty crude. At least it should implement copying only references
     # to the original data in case it's big. Now it copies the data for output.
     out=[]
     if case:
         for term in list:
             if term.find(pat)>-1: out.append(term)
     else:
         lpat=pat.lower()
         for term in list:
             if term.lower().find(lpat)>-1: out.append(term)
 
     if len(out): return out
     else: return None
 
 #----------------------------------------------------------------------------
 def dgrep(pat,*opts):
     """Return grep() on dir()+dir(__builtins__).
 
     A very common use of grep() when working interactively."""
 
     return grep(pat,dir(__main__)+dir(__main__.__builtins__),*opts)
 
 #----------------------------------------------------------------------------
 def idgrep(pat):
     """Case-insensitive dgrep()"""
 
     return dgrep(pat,0)
 
 #----------------------------------------------------------------------------
 def igrep(pat,list):
     """Synonym for case-insensitive grep."""
 
     return grep(pat,list,case=0)
 
 #----------------------------------------------------------------------------
 def indent(str,nspaces=4,ntabs=0):
     """Indent a string a given number of spaces or tabstops.
     
     indent(str,nspaces=4,ntabs=0) -> indent str by ntabs+nspaces.
     """
     if str is None:
         return
     ind = '\t'*ntabs+' '*nspaces
     outstr = '%s%s' % (ind,str.replace(os.linesep,os.linesep+ind))
     if outstr.endswith(os.linesep+ind):
         return outstr[:-len(ind)]
     else:
         return outstr
     
 #-----------------------------------------------------------------------------
 def native_line_ends(filename,backup=1):
     """Convert (in-place) a file to line-ends native to the current OS.
 
     If the optional backup argument is given as false, no backup of the
     original file is left.  """
 
     backup_suffixes = {'posix':'~','dos':'.bak','nt':'.bak','mac':'.bak'}
 
     bak_filename = filename + backup_suffixes[os.name]
 
     original = open(filename).read()
     shutil.copy2(filename,bak_filename)
     try:
         new = open(filename,'wb')
         new.write(os.linesep.join(original.splitlines()))
         new.write(os.linesep) # ALWAYS put an eol at the end of the file
         new.close()
     except:
         os.rename(bak_filename,filename)
     if not backup:
         try:
             os.remove(bak_filename)
         except:
             pass
     
 #----------------------------------------------------------------------------
 def get_pager_cmd(pager_cmd = None):
     """Return a pager command.
 
     Makes some attempts at finding an OS-correct one."""
     
     if os.name == 'posix':
         default_pager_cmd = 'less -r'  # -r for color control sequences
     elif os.name in ['nt','dos']:
         default_pager_cmd = 'type'
 
     if pager_cmd is None:
         try:
             pager_cmd = os.environ['PAGER']
         except:
             pager_cmd = default_pager_cmd
     return pager_cmd
 
 #-----------------------------------------------------------------------------
 def get_pager_start(pager,start):
     """Return the string for paging files with an offset.
 
     This is the '+N' argument which less and more (under Unix) accept.
     """
 
     if pager in ['less','more']:
         if start:
             start_string = '+' + str(start)
         else:
             start_string = ''
     else:
         start_string = ''
     return start_string
 
 #----------------------------------------------------------------------------
 if os.name == "nt":
     import msvcrt
     def page_more():
         """ Smart pausing between pages
 
         @return:    True if need print more lines, False if quit
         """
         Term.cout.write('---Return to continue, q to quit--- ')
         ans = msvcrt.getch()
         if ans in ("q", "Q"):
             result = False
         else:
             result = True
         Term.cout.write("\b"*37 + " "*37 + "\b"*37)
         return result
 else:
     def page_more():
         ans = raw_input('---Return to continue, q to quit--- ')
         if ans.lower().startswith('q'):
             return False
         else:
             return True
 
 esc_re = re.compile(r"(\x1b[^m]+m)")
 
 def page_dumb(strng,start=0,screen_lines=25):
     """Very dumb 'pager' in Python, for when nothing else works.
 
     Only moves forward, same interface as page(), except for pager_cmd and
     mode."""
 
     out_ln  = strng.splitlines()[start:]
     screens = chop(out_ln,screen_lines-1)
     if len(screens) == 1:
         print >>Term.cout, os.linesep.join(screens[0])
     else:
         last_escape = ""
         for scr in screens[0:-1]:
             hunk = os.linesep.join(scr)
             print >>Term.cout, last_escape + hunk
             if not page_more():
                 return
             esc_list = esc_re.findall(hunk)
             if len(esc_list) > 0:
                 last_escape = esc_list[-1]
         print >>Term.cout, last_escape + os.linesep.join(screens[-1])
 
 #----------------------------------------------------------------------------
 def page(strng,start=0,screen_lines=0,pager_cmd = None):
     """Print a string, piping through a pager after a certain length.
 
     The screen_lines parameter specifies the number of *usable* lines of your
     terminal screen (total lines minus lines you need to reserve to show other
     information).
 
     If you set screen_lines to a number <=0, page() will try to auto-determine
     your screen size and will only use up to (screen_size+screen_lines) for
     printing, paging after that. That is, if you want auto-detection but need
     to reserve the bottom 3 lines of the screen, use screen_lines = -3, and for
     auto-detection without any lines reserved simply use screen_lines = 0.
 
     If a string won't fit in the allowed lines, it is sent through the
     specified pager command. If none given, look for PAGER in the environment,
     and ultimately default to less.
 
     If no system pager works, the string is sent through a 'dumb pager'
     written in python, very simplistic.
     """
     
     # Ugly kludge, but calling curses.initscr() flat out crashes in emacs
     TERM = os.environ.get('TERM','dumb')
     if TERM in ['dumb','emacs'] and os.name != 'nt':
         print strng
         return
     # chop off the topmost part of the string we don't want to see
     str_lines = strng.split(os.linesep)[start:]
     str_toprint = os.linesep.join(str_lines)
     num_newlines = len(str_lines)
     len_str = len(str_toprint)
     
     # Dumb heuristics to guesstimate number of on-screen lines the string
     # takes.  Very basic, but good enough for docstrings in reasonable
     # terminals. If someone later feels like refining it, it's not hard.
     numlines = max(num_newlines,int(len_str/80)+1)
 
     if os.name == "nt":
         screen_lines_def = get_console_size(defaulty=25)[1]
     else:
         screen_lines_def = 25 # default value if we can't auto-determine
 
     # auto-determine screen size
     if screen_lines <= 0:
         if TERM=='xterm':
             try:
                 import curses
                 if hasattr(curses,'initscr'):
                     use_curses = 1
                 else:
                     use_curses = 0
             except ImportError:
                 use_curses = 0
         else:
             # curses causes problems on many terminals other than xterm.
             use_curses = 0
         if use_curses:
                 scr = curses.initscr()
                 screen_lines_real,screen_cols = scr.getmaxyx()
                 curses.endwin()
                 screen_lines += screen_lines_real
                 #print '***Screen size:',screen_lines_real,'lines x',\
                 #screen_cols,'columns.' # dbg
         else:
                 screen_lines += screen_lines_def
 
     #print 'numlines',numlines,'screenlines',screen_lines  # dbg
     if numlines <= screen_lines :
         #print '*** normal print'  # dbg
         print >>Term.cout, str_toprint
     else:
         # Try to open pager and default to internal one if that fails.
         # All failure modes are tagged as 'retval=1', to match the return
         # value of a failed system command.  If any intermediate attempt
         # sets retval to 1, at the end we resort to our own page_dumb() pager.
         pager_cmd = get_pager_cmd(pager_cmd)
         pager_cmd += ' ' + get_pager_start(pager_cmd,start)
         if os.name == 'nt':
             if pager_cmd.startswith('type'):
                 # The default WinXP 'type' command is failing on complex strings.
                 retval = 1
             else:
                 tmpname = tempfile.mktemp('.txt')
                 tmpfile = file(tmpname,'wt')
                 tmpfile.write(strng)
                 tmpfile.close()
                 cmd = "%s < %s" % (pager_cmd,tmpname)
                 if os.system(cmd):
                   retval = 1
                 else:
                   retval = None
                 os.remove(tmpname)
         else:
             try:
                 retval = None
                 # if I use popen4, things hang. No idea why.
                 #pager,shell_out = os.popen4(pager_cmd)
                 pager = os.popen(pager_cmd,'w')
                 pager.write(strng)
                 pager.close()
                 retval = pager.close()  # success returns None
             except IOError,msg:  # broken pipe when user quits
                 if msg.args == (32,'Broken pipe'):
                     retval = None
                 else:
                     retval = 1
             except OSError:
                 # Other strange problems, sometimes seen in Win2k/cygwin
                 retval = 1
         if retval is not None:
             page_dumb(strng,screen_lines=screen_lines)
 
 #----------------------------------------------------------------------------
 def page_file(fname,start = 0, pager_cmd = None):
     """Page a file, using an optional pager command and starting line.
     """
 
     pager_cmd = get_pager_cmd(pager_cmd)
     pager_cmd += ' ' + get_pager_start(pager_cmd,start)
 
     try:
         if os.environ['TERM'] in ['emacs','dumb']:
             raise EnvironmentError
         xsys(pager_cmd + ' ' + fname)
     except:
         try:
             if start > 0:
                 start -= 1
             page(open(fname).read(),start)
         except:
             print 'Unable to show file',`fname`
 
 #----------------------------------------------------------------------------
 def snip_print(str,width = 75,print_full = 0,header = ''):
     """Print a string snipping the midsection to fit in width.
 
     print_full: mode control:
       - 0: only snip long strings
       - 1: send to page() directly.
       - 2: snip long strings and ask for full length viewing with page()
     Return 1 if snipping was necessary, 0 otherwise."""
 
     if print_full == 1:
         page(header+str)
         return 0
 
     print header,
     if len(str) < width:
         print str
         snip = 0
     else:
         whalf = int((width -5)/2)
         print str[:whalf] + ' <...> ' + str[-whalf:]
         snip = 1
     if snip and print_full == 2:
         if raw_input(header+' Snipped. View (y/n)? [N]').lower() == 'y':
             page(str)
     return snip
 
 #****************************************************************************
 # lists, dicts and structures
 
 def belong(candidates,checklist):
     """Check whether a list of items appear in a given list of options.
 
     Returns a list of 1 and 0, one for each candidate given."""
 
     return [x in checklist for x in candidates]
 
 #----------------------------------------------------------------------------
 def uniq_stable(elems):
     """uniq_stable(elems) -> list
 
     Return from an iterable, a list of all the unique elements in the input,
     but maintaining the order in which they first appear.
 
     A naive solution to this problem which just makes a dictionary with the
     elements as keys fails to respect the stability condition, since
     dictionaries are unsorted by nature.
 
     Note: All elements in the input must be valid dictionary keys for this
     routine to work, as it internally uses a dictionary for efficiency
     reasons."""
     
     unique = []
     unique_dict = {}
     for nn in elems:
         if nn not in unique_dict:
             unique.append(nn)
             unique_dict[nn] = None
     return unique
 
 #----------------------------------------------------------------------------
 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]
             if type(elem)==type([]):
                 self.depth += 1
                 self.__call__(elem,itpl('$pos$idx,'),**kw)
                 self.depth -= 1
             else:
                 printpl(kw['indent']*self.depth+'$pos$idx$kw["sep"]$elem')
 
 nlprint = NLprinter()
 #----------------------------------------------------------------------------
 def all_belong(candidates,checklist):
     """Check whether a list of items ALL appear in a given list of options.
 
     Returns a single 1 or 0 value."""
 
     return 1-(0 in [x in checklist for x in candidates])
 
 #----------------------------------------------------------------------------
 def sort_compare(lst1,lst2,inplace = 1):
     """Sort and compare two lists.
 
     By default it does it in place, thus modifying the lists. Use inplace = 0
     to avoid that (at the cost of temporary copy creation)."""
     if not inplace:
         lst1 = lst1[:]
         lst2 = lst2[:]
     lst1.sort(); lst2.sort()
     return lst1 == lst2
 
 #----------------------------------------------------------------------------
 def mkdict(**kwargs):
     """Return a dict from a keyword list.
 
     It's just syntactic sugar for making ditcionary creation more convenient:
     # the standard way
     >>>data = { 'red' : 1, 'green' : 2, 'blue' : 3 }
     # a cleaner way
     >>>data = dict(red=1, green=2, blue=3)
 
     If you need more than this, look at the Struct() class."""
 
     return kwargs
 
 #----------------------------------------------------------------------------
 def list2dict(lst):
     """Takes a list of (key,value) pairs and turns it into a dict."""
 
     dic = {}
     for k,v in lst: dic[k] = v
     return dic
 
 #----------------------------------------------------------------------------
 def list2dict2(lst,default=''):
     """Takes a list and turns it into a dict.
     Much slower than list2dict, but more versatile. This version can take
     lists with sublists of arbitrary length (including sclars)."""
 
     dic = {}
     for elem in lst:
         if type(elem) in (types.ListType,types.TupleType):
             size = len(elem)
             if  size == 0:
                 pass
             elif size == 1:
                 dic[elem] = default
             else:
                 k,v = elem[0], elem[1:]
                 if len(v) == 1: v = v[0]
                 dic[k] = v
         else:
             dic[elem] = default
     return dic
 
 #----------------------------------------------------------------------------
 def flatten(seq):
     """Flatten a list of lists (NOT recursive, only works for 2d lists)."""
 
     return [x for subseq in seq for x in subseq]
 
 #----------------------------------------------------------------------------
 def get_slice(seq,start=0,stop=None,step=1):
     """Get a slice of a sequence with variable step. Specify start,stop,step."""
     if stop == None:
         stop = len(seq)
     item = lambda i: seq[i]
     return map(item,xrange(start,stop,step))
 
 #----------------------------------------------------------------------------
 def chop(seq,size):
     """Chop a sequence into chunks of the given size."""
     chunk = lambda i: seq[i:i+size]
     return map(chunk,xrange(0,len(seq),size))
 
 #----------------------------------------------------------------------------
 # with is a keyword as of python 2.5, so this function is renamed to withobj
 # from its old 'with' name.
 def with_obj(object, **args):
     """Set multiple attributes for an object, similar to Pascal's with.
 
     Example:
     with_obj(jim,
              born = 1960,
              haircolour = 'Brown',
              eyecolour = 'Green')
 
     Credit: Greg Ewing, in
     http://mail.python.org/pipermail/python-list/2001-May/040703.html.
 
     NOTE: up until IPython 0.7.2, this was called simply 'with', but 'with'
     has become a keyword for Python 2.5, so we had to rename it."""
 
     object.__dict__.update(args)
 
 #----------------------------------------------------------------------------
 def setattr_list(obj,alist,nspace = None):
     """Set a list of attributes for an object taken from a namespace.
 
     setattr_list(obj,alist,nspace) -> sets in obj all the attributes listed in
     alist with their values taken from nspace, which must be a dict (something
     like locals() will often do) If nspace isn't given, locals() of the
     *caller* is used, so in most cases you can omit it.
 
     Note that alist can be given as a string, which will be automatically
     split into a list on whitespace. If given as a list, it must be a list of
     *strings* (the variable names themselves), not of variables."""
 
     # this grabs the local variables from the *previous* call frame -- that is
     # the locals from the function that called setattr_list().
     # - snipped from weave.inline()
     if nspace is None:
         call_frame = sys._getframe().f_back
         nspace = call_frame.f_locals
 
     if type(alist) in StringTypes:
         alist = alist.split()
     for attr in alist:
         val = eval(attr,nspace)
         setattr(obj,attr,val)
 
 #----------------------------------------------------------------------------
 def getattr_list(obj,alist,*args):
     """getattr_list(obj,alist[, default]) -> attribute list.
 
     Get a list of named attributes for an object. When a default argument is
     given, it is returned when the attribute doesn't exist; without it, an
     exception is raised in that case.
 
     Note that alist can be given as a string, which will be automatically
     split into a list on whitespace. If given as a list, it must be a list of
     *strings* (the variable names themselves), not of variables."""
 
     if type(alist) in StringTypes:
         alist = alist.split()
     if args:
         if len(args)==1:
             default = args[0]
             return map(lambda attr: getattr(obj,attr,default),alist)
         else:
             raise ValueError,'getattr_list() takes only one optional argument'
     else:
         return map(lambda attr: getattr(obj,attr),alist)
     
 #----------------------------------------------------------------------------
 def map_method(method,object_list,*argseq,**kw):
     """map_method(method,object_list,*args,**kw) -> list
 
     Return a list of the results of applying the methods to the items of the
     argument sequence(s).  If more than one sequence is given, the method is
     called with an argument list consisting of the corresponding item of each
     sequence. All sequences must be of the same length.
 
     Keyword arguments are passed verbatim to all objects called.
 
     This is Python code, so it's not nearly as fast as the builtin map()."""
 
     out_list = []
     idx = 0
     for object in object_list:
         try:
             handler = getattr(object, method)
         except AttributeError:
             out_list.append(None)
         else:
             if argseq:
                 args = map(lambda lst:lst[idx],argseq)
                 #print 'ob',object,'hand',handler,'ar',args # dbg
                 out_list.append(handler(args,**kw))
             else:
                 out_list.append(handler(**kw))
         idx += 1
     return out_list
 
 #----------------------------------------------------------------------------
 def import_fail_info(mod_name,fns=None):
     """Inform load failure for a module."""
 
     if fns == None:
         warn("Loading of %s failed.\n" % (mod_name,))
     else:
         warn("Loading of %s from %s failed.\n" % (fns,mod_name))
 
 #----------------------------------------------------------------------------
 # Proposed popitem() extension, written as a method
 
 
 class NotGiven: pass
 
 def popkey(dct,key,default=NotGiven):
     """Return dct[key] and delete dct[key].
 
     If default is given, return it if dct[key] doesn't exist, otherwise raise
     KeyError.  """
 
     try:
         val = dct[key]
     except KeyError:
         if default is NotGiven:
             raise
         else:
             return default
     else:
         del dct[key]
         return val
 
 def wrap_deprecated(func, suggest = '<nothing>'):
     def newFunc(*args, **kwargs):
         warnings.warn("Call to deprecated function %s, use %s instead" % 
                       ( func.__name__, suggest),
                       category=DeprecationWarning,
                       stacklevel = 2)
         return func(*args, **kwargs)
     return newFunc
     
 #*************************** end of file <genutils.py> **********************