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
import sys

# 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 = []

# 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.)
    def db(line):
        line = line + "\n"
        with open("debugging.txt","a") as f:
            f.write(line)


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

    # Expand the user name "~" if it is in line.  It does not necessarily exist.
    line = os.path.expanduser(line)

    # REMEMBER TO EXPAND ALL PATHS.

    if line == "":
        # Use the working directory to start.
        directory = os.path.abspath(".")
        basename = ""


    # Split the line into base name (blah.txt) and directory (/home/jenny
    # without the end slash).  "/home" has base name "home" and directory "/".
    # "/home/" has base name "" and directory "/home".

    else:
        base_name = os.path.basename(line)
        directory = os.path.dirname(line)
        if directory == "":
            directory = os.path.abspath(".")
        db("dir " + directory + "  base " + base_name + " line " + line)

    if os.path.exists(directory):
        if os.path.isdir(directory):
            base_name = ""
            if not line.endswith("/"):
                directory = directory + "/"

    if not os.path.exists(directory):
        possible_completions = []

    else:
        # Find all files in this directory.
        possible_completions = os.listdir(directory)

    db(line + "   " + str(possible_completions))

    for one in possible_completions:
        if state < len(possible_completions):
            if line in one or line == "" or line == directory or basename in one:
                return one
        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.