import hashlib


def hash_file(path, block_size=65536):
    """Returns SHA256 checksum of a file

    Args:
        path (string): Absolute file path of file to hash

        block_size (int, optional): Number of bytes to read per block
    """
    sha256 = hashlib.sha256()
    with open(path, 'rb') as f:
        for block in iter(lambda: f.read(block_size), b''):
            sha256.update(block)
    return sha256.hexdigest()