rotate_files.py

import os
import glob
import shutil

def rotate_files(filename, limit):
    need_rotate = os.path.exists(filename)
    if not need_rotate:
        return
    files = glob.glob('%s.*' % filename)
    files.sort(key=lambda f: int(f.rsplit('.', 1)[1]))
    files.insert(0, filename)
    num_files = len(files)
    if num_files <= limit:
        files.append('%s.%d' % (filename, num_files))
    start = min(num_files-1, limit-1)
    while start >= 0:
        src, dest = files[start], files[start+1]
        shutil.move(src, dest)
        start -= 1