Batch rename tool using regex

renametool.py

from argparse import ArgumentParser
from re import compile as _re_compile
from pathlib import Path
from os import walk
from sys import exit

def iterdir(root, recursive = False):
    if not recursive:
        yield from Path(root).iterdir()
        return
    
    for dirpath, dirnames, filenames in walk(root):
        for filename in filenames:
            yield Path(dirname) / filename

def match_strategy(arg):
    if arg=="full":
        return "fullmatch"
    elif arg=="start":
        return "match"
    elif arg in ("any","anywhere"):
        return "search"

parser = ArgumentParser(description="Renames files in a directory by regex-based rules")
parser.add_argument("input_pattern",help="The pattern that matches the files you wish to rename.")
parser.add_argument("output",help="What you wish to rename these files to. Can use backreferences.")
parser.add_argument("-d","--dry-run",action="store_true",help="Show what files would be moved, and to where, but not actually do it.")
parser.add_argument("-r","--recursive",action="store_true",help="Recurse into subdirectories.")
parser.add_argument("-t","-root",dest="root",default=".",help="The root of the rename operation.")
parser.add_argument("-c","--on-conflict",choices=["error", "skip"],default="error",help="What to do if renaming a file would cause it to overwrite another file.")
parser.add_argument("-m","--match",choices=["full", "start", "any", "anywhere"],default="full",type=match_strategy,help="How to match the pattern against the filenames.")
args = parser.parse_args()
print(args)

pattern = _re_compile(args.input_pattern)
match = getattr(pattern, args.match)
for path in iterdir(args.root, args.recursive):
    if not path.is_file(): continue
    
    if not (m:=match(path.name)): continue
    
    new_name = m.expand(args.output)
    target = path.with_name(new_name)
    
    if target.exists():
        print(f"Cannot move {path} to {target} (target exists!)")
        if args.on_conflict=="error":
            exit(1)
    
    print(f"{path} -> {target}")
    if not args.dry_run: path.rename(target)