Tiny cp command with -r option in python 3.6

cp.py

  #! /usr/local/bin/python3.7

import sys
import argparse
from pathlib import Path
from os import path, makedirs


def read_file(file_path, chunksize=8192):
    with open(file_path, mode='rb') as f:
        while True:
            chunk = f.read(chunksize)
            if chunk:
                yield chunk
            else:
                break


def copy_file(src_file_path, dst_file_path, is_recursive=False):
    if path.isdir(src_file_path):
        print(
            src_file_path,
            'is a directory!\nUse --recursive for directories'
        )
        return
    src_dir_path, src_file_name = path.split(src_file_path)
    dst_dir_path, dst_file_name = path.split(dst_file_path)

    if dst_file_name is None or path.isdir(dst_file_name):
        dst_file_name = src_file_name
    dst_file_path = path.join(dst_dir_path, dst_file_name)
    try:
        if is_recursive:
            makedirs(path.dirname(dst_file_path), exist_ok=True)
        f = open(dst_file_path, mode='wb')
    except (FileNoFoundError, PermissionError) as ex:
        print(ex)
        exit(-1)

    try:
        for chunk in read_file(src_file_path):
            f.write(chunk)
    except OSError as ex:
        print(ex)
    finally:
        f.close()
        return


if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument('SOURCE')
    parser.add_argument('DEST')
    parser.add_argument(
        '-r',
        '--recursive',
        help='copy directories recursively',
        action='store_true',
    )
    args = parser.parse_args()
    src_path = path.abspath(args.SOURCE)
    dst_path = path.abspath(args.DEST)
    if src_path in dst_path:
        print(f"cp: cannot copy a directory, "
              f"'{src_path}', into itself, "
              f"'{dst_path}'")
        exit(-1)

    if not args.recursive:
        copy_file(src_path, dst_path)
        exit(0)

    for file in Path(src_path).glob('**/*'):
        src_dir_path, src_file_name = path.split(file)
        dst_path = path.join(
            args.DEST,
            path.relpath(src_dir_path, args.SOURCE),
            src_file_name
        )
        if path.isdir(file):
            continue
        copy_file(file, dst_path, True)

    exit(0)