Tab-completion in Python interpreter in OS X Terminal

Question

Several months ago, I wrote a blog post detailing how to achieve tab-completion in the standard Python interactive interpreter--a feature I once thought only available in IPython. I've found it tremendously handy given that I sometimes have to switch to the standard interpreter due to IPython unicode issues.

Recently I've done some work in OS X. To my discontent, the script doesn't seem to work for OS X's Terminal application. I'm hoping some of you with experience in OS X might be able to help me trouble-shoot it so it can work in Terminal, as well.

I am reproducing the code below

import atexit
import os.path

try:
    import readline
except ImportError:
    pass
else:
    import rlcompleter

    class IrlCompleter(rlcompleter.Completer):
        """
        This class enables a "tab" insertion if there's no text for
        completion.

        The default "tab" is four spaces. You can initialize with '\t' as
        the tab if you wish to use a genuine tab.

        """

        def __init__(self, tab='    '):
            self.tab = tab
            rlcompleter.Completer.__init__(self)


        def complete(self, text, state):
            if text == '':
                readline.insert_text(self.tab)
                return None
            else:
                return rlcompleter.Completer.complete(self,text,state)


    #you could change this line to bind another key instead tab.
    readline.parse_and_bind('tab: complete')
    readline.set_completer(IrlCompleter('\t').complete)


# Restore our command-line history, and save it when Python exits.
history_path = os.path.expanduser('~/.pyhistory')
if os.path.isfile(history_path):
    readline.read_history_file(history_path)
atexit.register(lambda x=history_path: readline.write_history_file(x))

Note that I have slightly edited it from the version on my blog post so that the IrlCompleter is initialized with a true tab, which seems to be what is output by the Tab key in Terminal.

Answer 1

To avoid having to use more GPL code, Apple doesn't include a real readline. Instead it uses the BSD-licensed libedit, which is only mostly-readline-compatible. Build your own Python (or use Fink or MacPorts) if you want completion.