Half-working filename tab-completer. Play with it--it mostly works, but you have to help it along more than you're used to at the command line.

simple_file_completer.py

#!/usr/bin/env python
import readline
import os
import re

# This will tab-complete from the working directory, starting from /, and going
# through the sub-directories, but it doesn't behave quite the way you expect.
# For instance, it chooses for you if there are two partial matches.  

# The readline call to def complete_path does not pass a leading "/" in the "text"
# variable, so I had to start using get_line_buffer and really don't find much
# use for the variables "text" and "state".  

#RE_SPACE = re.compile(".*\s+$", re.M)  # Not sure what this does.

possible_completions = os.listdir(".")

# This will be changed to a class, so that the list possible_completions can be saved
# between calls, rather than using a global definition.

def complete_path(text, state):

    # NOTE THAT THE LEADING / WILL NOT COME THROUGH IN text.  This is why only
    # the line buffer is used below, not the "text" field passed from readline.
    
    # Changed the type of "line" to a string.  (It was a list in the last
    # version.)

    line = readline.get_line_buffer()
    print "\n" + str(line) + "\n"

    try:
        if line == "":

            # Nothing has been typed yet, so the default starting path is the
            # working directory.

            possible_completions = os.listdir(".")

        elif not "/" in line:
            
            # The line is not empty, but does not contain a "/".  This must be
            # a partial file name in the working directory.

            temporary_completion_list = os.listdir(".")

            # Keep only the entries where the last sub-string after
            # the last "/" matches partial_file_name.

            possible_completions = []
            for one_item in temporary_completion_list:
                this_partial_file_name = one_item.rsplit("/",1)[1]
                if this_partial_file_name == line:
                    possible_completions.append(one_item)

        else:

            # Need to treat a path that refers to a directory, as well as one
            # that refers to a file or partial file name.

            try:

                # Assume that the line typed so far is a directory, and try to
                # get a listing of its contents.  This will handle either e.g.
                # /home/jenny/mydir/ or /home/jenny/mydir

                possible_completions = os.listdir(line)

            except:

                # In the final version, examine the exception--error 20 from os
                # is "Not a directory" and will elucidate the problem.

                # See if the path is a directory followed by a file name or
                # partial file name.  e.g. "/home/jenny/mydir/blah": if the
                # path does not end in "/", strip off everything to the right
                # of the last "/", and see if that is a valid directory.

                if not line.endswith("/"):
                    
                    # If it ends with "/", then it must be a directory name
                    # (valid or not).

                    try:

                        # Strip off the last word.
                        # Example:  /home/jenny/mydir/blah --> /home/jenny/mydir/

                        path, partial_file_name = line.rsplit("/",1)
                        temporary_completion_list = os.listdir(path)

                        # Keep only the entries where the last sub-string after
                        # the last "/" matches partial_file_name.

                        possible_completions = []
                        for one_item in temporary_completion_list:
                            this_partial_file_name = one_item.rsplit("/",1)[1]
                            if this_partial_file_name == partial_file_name:
                                possible_completions.append(one_item)

                        ### This is repeated code and can be moved to another
                        ### method.

                    except:
                        
                        # /home/jenny/mydir/ was not a valid directory.

                        try:
                            
                            # See if the line refers to a directory followed by a 

                    # If nothing works, don't try any more completion.  The
                    # user will have to fix the path.
                    pass


    except:
        pass

    for one_file in possible_completions:
        if one_file.startswith(text) and state == 0:
            return one_file
        else:
            state -= 1


print os.listdir("/home/hayes/testing.py")
readline.parse_and_bind("tab: complete")
readline.set_completer(complete_path)
while True:
    file_name = raw_input("Enter file name: ")
    print file_name
    

There's a new working version in good shape on gist https://gist.github.com/4040404/ with credits in the comments.