<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def hash_file(file_path, block_size = 65536):
 """ Hashes a file with sha256 """

    sha = hashlib.sha256()
    with open(file_path, 'rb') as h_file:
        file_buffer = h_file.read(block_size)
        while len(file_buffer) > 0:
            sha.update(file_buffer)
            file_buffer = h_file.read(block_size)
    return sha.hexdigest()