manga mass-renaming script

import os
import sys
import re
import argparse

parser = argparse.ArgumentParser()
parser.add_argument('-n', dest='name', help='name of the manga')
parser.add_argument('--prompt', action='store_true', help='prompt for each filename update confirmation')
args = parser.parse_args()

# Regex blocks
if args.name is not None:
    re_named_full = r'^'+args.name+' [0-9]{2,4}' # regex for 'full' chapter, with name
    re_named_half = r'^'+args.name+' [0-9]{2,4}.[0-9]{1}' # regex for 'half' chapter (e.g. 12.5), with name
re_noname_full = r'^[A-Za-z \-!?]* [0-9]{2,4} '
re_noname_half = r'^[A-Za-z \-!?]* [0-9]{2,4}.[0-9]{1,2} '
re_noname_already_valid_full = r'^[A-Za-z \-!?]*[0-9]{2,4}.cbz$'
re_noname_already_valid_half = r'^[A-Za-z \-!?]*[0-9]{2,4}.[0-9]{1,2}.cbz$'

if args.name is None:
    print('No name supplied via args. Attempting automatic name detection...')

#using os.listdir and os.rename to make files ready for manga server
files = os.listdir('./')
for f in files:

    if f == 'rename.py': # skip the script file
        continue

    # Make .zip files into .cbz
    if re.search(r'.zip$', f):
        filename = f[:-4] + '.cbz'
        os.rename(f, filename)
        f = filename

    # Remove any tags in square brackets
    filename = re.sub('\[.*\]', '', f)
    if filename is not f:
        os.rename(f, filename)
        f = filename

    # Replace underscores with spaces
    filename = f.replace('_', ' ')
    if filename is not f:
        os.rename(f, filename)
        f = filename

    # Expand any single, standalone numbers into 2-digit numbers for name inclusion
    if re.search(r' [0-9] ', f, 1):
        number = re.search(r' [0-9] ', f, 1).group().strip()
        filename = filename.replace(' '+number+' ', ' 0'+number+' ')
        os.rename(f, filename)
        f = filename

    # If the filename already conforms to "<name> <chapter>.cbz", skip
    if args.name is not None:
        if re.search(re_named_full+'.cbz$', f) or re.search(re_named_half+'.cbz$', f):
            continue
    else:
        if re.search(re_noname_already_valid_full, f) or re.search(re_noname_already_valid_half, f):
            continue

    # A name was supplied in the arguments (for folders with one series)
    if args.name is not None:

        # Check for 'full' chapter substring
        if re.search(re_string_plain+' ', f):
            chapter = re.search(re_named_full+' ', f).group().strip() + '.cbz'
            print('Renaming to: '+chapter)
            if args.prompt:
                response = input('Proceed with rename? [y/n]: ')
                if response == 'n' or response == 'N':
                    continue
            os.rename(f, chapter)
        # Check for 'half' chapter substring
        elif re.search(re_string_halfchapter+' ', f):
            chapter = re.search(re_named_half+' ', f).group().strip() + '.cbz'
            print('Renaming to: '+chapter)
            if args.prompt:
                response = input('Proceed with rename? [y/n]: ')
                if response == 'n' or response == 'N':
                    continue
            os.rename(f, chapter)

    # A name was not supplied in the arguments (for folders with multiple series/ oneshots)
    else:
        name = re.search(re_noname_full, f)
        if name is None:
            name = re.search(re_noname_half, f)
            if name is None:

                # Offer manual renaming
                print('Name detection failed for: '+f)
                if args.prompt:
                    response = input('Manually rename? [y/n]:')
                    if response == 'y' or response == 'Y':
                        name = input('Enter filename: ')
                        if '.cbz' not in name:
                            name += '.cbz'
                        os.rename(f, name)
                        continue
                else:
                    continue
        if name is not None:
            filename = name.group().strip() + '.cbz'
            print('Name detected: ' + filename)
            if args.prompt:
                response = input('Proceed with rename? [y/n]: ')
                if response == 'n' or response == 'N':
                    continue
            os.rename(f, filename)