renaming sequentially

May 1st, 2008

If you've been dealing with files for a while you will have noticed that there is a slight semantic gap between how humans see files and how computers do. If you've ever seen a file list like this you know what I mean:


Numbering these files was done in good faith, and a user understands what it means, but the computer doesn't get it. Sorting in dictionary order produces the wrong order as far as the user is concerned. The reason is that the digits in these filenames are not treated and compared as integers, merely as strings. (Actually, . comes before 0 in ASCII, what's going on here?)

While we're not expecting our computers to wisen up about this anytime soon, there is the obvious fix:


You've probably done this by hand once or twice, while cursing.

On the upshot, this is very easy to fix with a few lines of code:

#!/usr/bin/env python
# Author: Martin Matusiak <>
# Licensed under the GNU Public License, version 3.
# revision 1 - support multiple digit runs in filenames

import os, string, glob, re, sys

def renseq():
    if (len(sys.argv) != 2):
        print "Usage:\t" + sys.argv[0] + " <num_digits>"

def ren_seq_files(num_digits):
    files = glob.glob("*")
    for filename in files:
        m ="(.*)(\..*)", filename)
        ext = ""
        if m: (filename, ext) = m.groups()

        digit_runs = re.finditer("([0-9]+)", filename)
        spans = [m.span() for m in digit_runs if digit_runs]
        if spans:
            arr = list(filename)
            for (s, e) in spans:
                arr[s:e] = string.zfill(str( int(filename[s:e]) ), int(num_digits))
            os.rename(filename+ext, "".join(arr)+ext)

if __name__ == "__main__":

This works on all the files in the current directory. Pass an integer to and it will change all the numbers in a filename (if there are any) to the same numbers, padded with zeros if they have fewer digits than the amount you want. So on the example 2

will turn the first list into the second list.

If say, there are filenames with numbers of three digits and you pass 2 to, the numbers will be preserved (so it's not a destructive rename), you'll just revert to your incorrect ordering as it was in the beginning. will rewrite all the numbers in a filename, but not the extension. So mp3 won't become mp03. ;)

:: random entries in this category ::

8 Responses to "renaming sequentially"

  1. erik says:

    "You’ve probably done this by hand once or twice, while cursing."

    lol yes :D

  2. Ciaran McCreesh says:

    for a in $(seq 1 9 ) ; do mv Lecture${a}.pdf Lecture0${a}.pdf ; done

  3. Patrick says:

    There is a nice KDE application for that task: kde-misc/krename (

  4. numerodix says:

    Yes, for the simplest possible case. But when you have a hundreds or thousands of files that becomes pretty messy, because different filenames will need different amounts of padding, ie. 1 => 0001 vs 100 => 0100.

  5. numerodix says:

    I'm not so crazy about mission control type of renamers. I takes me longer to figure out how to do something than just do it in the shell. Maybe it's just me.

  6. Ciaran McCreesh says:

    For four digits:

    for a in $(seq -f '%04.0f' 1 999 ) ; do mv -u Lecture${a##+(0)}.pdf Lecture${a}.pdf ; done

  7. Patrick says:

    numerodix: That's exactly what I thought - I do most file operations on the command line anyway. But then I gave it a try while I was using some random Live-CD and the program was in place anyway. With all the preview stuff and so on it's really helpful if you have complex renaming tasks.

  8. [...] leading zeros you want (and if you don’t say how many, it will find out on its own). Based on an old piece of code that has been [...]