source: python/vendor/Python-2.7.6/Tools/scripts/untabify.py

#! /usr/bin/env python

"Replace tabs with spaces in argument files.  Print names of changed files."

import os
import sys
import getopt

def main():
    tabsize = 8
    try:
        opts, args = getopt.getopt(sys.argv[1:], "t:")
        if not args:
            raise getopt.error, "At least one file argument required"
    except getopt.error, msg:
        print msg
        print "usage:", sys.argv[0], "[-t tabwidth] file ..."
        return
    for optname, optvalue in opts:
        if optname == '-t':
            tabsize = int(optvalue)

    for filename in args:
        process(filename, tabsize)

def process(filename, tabsize, verbose=True):
    try:
        f = open(filename)
        text = f.read()
        f.close()
    except IOError, msg:
        print "%r: I/O error: %s" % (filename, msg)
        return
    newtext = text.expandtabs(tabsize)
    if newtext == text:
        return
    backup = filename + "~"
    try:
        os.unlink(backup)
    except os.error:
        pass
    try:
        os.rename(filename, backup)
    except os.error:
        pass
    with open(filename, "w") as f:
        f.write(newtext)
    if verbose:
        print filename

if __name__ == '__main__':
    main()