Python function that computes checksum of a file using one of hashlib algorithms (default: SHA-256). It combines a "modern" implementation with a pre-Python3.11 compatible alternative.

get_checksum.py

from typing import Union
import hashlib
import os


def get_checksum(path_to_file: str, algorithm: Union[str, callable] = hashlib.sha256) -> str:
    """A function that computes checksum of a file using one of hashlib algorithms (default: SHA-256). It combines 
    a "modern" implementation with a pre-Python3.11 compatible alternative."""
    if not os.path.exists(path_to_file):
        raise FileNotFoundError(f"File {path_to_file!r} doesn't seem to exist")
    if hasattr(hashlib, 'file_digest'):
        with open(path_to_file, 'rb') as fh:
            return hashlib.file_digest(fh, algorithm).hexdigest()
    # Below is a pre-Python3.11 compatible alternative implementation. Source:
    # https://stackoverflow.com/questions/22058048/hashing-a-file-in-python/44873382#44873382
    h = algorithm()
    b  = bytearray(128*1024)
    mv = memoryview(b)
    with open(path_to_file, 'rb', buffering=0) as f:
        for n in iter(lambda: f.readinto(mv), 0):
            h.update(mv[:n])
    return h.hexdigest()