startup script for Python to enable tab completion

gistfile1.py

from sys import stdout, stderr

# Enable tab completion if readline is available. Rather than using the
# default completer, though, we allow tabs at the beginning of the line.
try:
   import readline
   readline.is_libedit = 'libedit' in readline.__doc__
except ImportError:
   pass
else:
   from rlcompleter import Completer

   class RZGCompleter(Completer):
      def complete(self, text, state):
         if readline.get_line_buffer().lstrip() == '':
            readline.insert_text('\t')
            if readline.is_libedit: stdout.write('\t')
            readline.redisplay()
            return None
         else:
            return Completer.complete(self, text, state)

   readline.set_completer(RZGCompleter().complete)

   if readline.is_libedit:
      # The OS X readline module wraps libedit. Unfortunately, it does so
      # poorly: tab completion only works at the beginning of the line. You
      # can install a working readline module with `easy_install readline`.
      print >> stderr, 'Note: Tab completion is borked with libedit.'
      readline.parse_and_bind('bind ^I rl_complete')
   else:
      readline.parse_and_bind('tab: complete')