make all files such as "dsf_kkk.jpg" into "kkk.jpg" in a specific folder

truncate.py

import os, re, sys

def sub_string(string, sub_str):
    """
    
    Arguments:
    - `string`: string you want to be truncated
    - `sub_str`: starting sub-string (exclusive)
    """
    index = string.rfind(sub_str)
    if index > 0 and index < len(string):
        return string[index + 1:]
    else:
        return string


def trim_cn(path):
    regx = re.compile("\\.jpg", re.IGNORECASE)
    name_list = filter (regx.search, os.listdir(path))
    for i in range(len(name_list)):
        name_list[i] = sub_string(name_list[i], "\\")

    for item in name_list:
        old = os.path.join(path, item)
        new = os.path.join(path, sub_string(item, "_"))
        os.rename(old, new)

    
def test_sub_string():
    """
    """
    slash_list = ["fdsf\\1.txt", "fds\\2.rmb", "kkkk\\3.mp3"]
    under_list = ["ff_1.txt", "fuiou_2.rmb", "mmm_3.mp3"]
    ac_list = ["1.txt", "2.rmb", "3.mp3"]

    for i in range(len(slash_list)):
        if ac_list[i] == sub_string(slash_list[i], "\\"):
            print "Test pass on: %s" % slash_list[i]
        else:
            print "Test FAIL!! on: %s" % slash_list[i]
        if ac_list[i] == sub_string(under_list[i], "_"):
            print "Test pass on: %s" % under_list[i]
        else:
            print "Test FAIL!! on: %s" % under_list[i]

def test():
    """
    """
    path = "/tmp/trimtest/"
    test_list = ["fdkf_1.jpg", "www_2.JPG"]
    ac_list = ["1.jpg", "2.JPG"]

    print "Generate list ..."
    for i in range(len(test_list)):
        f = open(os.path.join(path, test_list[i]), "w")
        f.close()
    
    trim_cn(path)

    for i in range(len(ac_list)):
        output = os.path.join(path, ac_list[i])
        if os.path.exists(output):
            print "Test pass on: %s" % ac_list[i]
            os.remove(output)
        else:
            print "Test FAIL!! on: %s" % ac_list[i]


if len(sys.argv) == 2:
    trim_cn(sys.argv[1])
else:
    print "Take a path as arguement ..."