Batch Renaming of Files in a Directory

Question

Is there an easy way to rename a group of files already contained in a directory, using Python?

Example: I have a directory full of *.doc files an

Answer 1

#  another regex version
#  usage example:
#  replacing an underscore in the filename with today's date
#  rename_files('..\\output', '(.*)(_)(.*\.CSV)', '\g<1>_20180402_\g<3>')
def rename_files(path, pattern, replacement):
    for filename in os.listdir(path):
        if re.search(pattern, filename):
            new_filename = re.sub(pattern, replacement, filename)
            new_fullname = os.path.join(path, new_filename)
            old_fullname = os.path.join(path, filename)
            os.rename(old_fullname, new_fullname)
            print('Renamed: ' + old_fullname + ' to ' + new_fullname