Use this script to add licence header to your python files.

licence_header_adder.py

import asyncio
import pathlib
import os
import time
import multiprocessing
from functools import wraps
from concurrent.futures.thread import ThreadPoolExecutor


executor = ThreadPoolExecutor(max_workers=multiprocessing.cpu_count() * 5)


def run_in_exc(func_):
    @wraps(func_)
    async def wrapper(*args, **kwargs):
        loop = asyncio.get_running_loop()
        return await loop.run_in_executor(executor, lambda: func_(*args, **kwargs))
    return wrapper

lisT = []

def file_list(path):
    pathlib.Path(path)
    for filepath in pathlib.Path(path).glob("**/*.*"):
        if os.path.isdir(filepath):file_list(filepath)
        elif os.path.isfile(filepath): 
            if not filepath in lisT:lisT.append(filepath.absolute())
    return lisT

print("\033[35m" + "Hi. Welcome To License Adder Tool!")
print("\033[35m" + "By : @AltruixDevs")

license_ = """# your licence header here"""
file_path = input("\033[31m" + "Enter Folder Path Containing your Python Files : \n")

while True:
    if os.path.isdir(file_path):
        break
    else:
        file_path = input("Try Again : [IS_NOT_A_DIR] Give me Valid Path. \n")
        if file_path == "exit":
            print("SCRIPT CLOSED.")
            exit()

@run_in_exc
def licence_file(file_path):
    file_as_read = open(file_path, "r")
    file_content = file_as_read.read()
    final_ = license_ + "\n\n" + file_content
    open_file_as_writer = open(file_path, "w")
    open_file_as_writer.write(final_)
    print("\033[92m" + f"Added Licence to : {str(file_path)}")

async def do_it():
    start_time = time.perf_counter()
    files_ = [i for i in file_list(file_path) if str(i).endswith(".py")]
    for i in files_:
        await licence_file(i)
    end_time = time.perf_counter()
    ms = round((end_time - start_time) * 1000, 2)
    print("\033[96m" + f"Tasked Completed in {ms} ms - Added Licence header in {len(files_)} Files.")


asyncio.run(do_it())