make file still readable after hashing in python

Question

I'm having this hash function for hashing an image with a new name:

def get_file_hash(file):
    """
    Returns a new filename based on the file content using MD5 hashing.
    It uses hashlib.md5() function from Python standard library to get
    the hash.

    Parameters
    ----------
    file : werkzeug.datastructures.FileStorage
        File sent by user.

    Returns
    -------
    str
        New filename based in md5 file hash.
    """
    hasher = hashlib.md5()
    basename = os.path.basename(file.filename)
    filename, extension = os.path.splitext(basename)
    file_read = file.read()
    hasher.update(file_read)
    processed_filename = hasher.hexdigest() + extension

    return processed_filename

and I'm not passing the last evaluation of this test (the one which says "Check the file content is still readable:"):

 def test_get_file_hash(self):
        filename = "tests/dog.jpeg"
        md5_filename = "0a7c757a80f2c5b13fa7a2a47a683593.jpeg"
        with open(filename, "rb") as fp:
            file = FileStorage(fp)

            # Check the new filename is correct
            new_filename = utils.get_file_hash(file)
            self.assertEqual(md5_filename, new_filename, new_filename)

            # Check the file content is still readable!
            self.assertTrue(file.read() != b"")

I don't know how to make that happen after I call the function, in context I implement the hash function and then save the image:

filename = utils.get_file_hash(img_api)
img_api.save("static/uploads/" + filename)

Any thoughts would be very much appreciated, best

Answer 1

Thanks you very much Mathias: this is how the function finally pass the test just in case:

def get_file_hash(file):
    """
    Returns a new filename based on the file content using MD5 hashing.
    It uses hashlib.md5() function from Python standard library to get
    the hash.

    Parameters
    ----------
    file : werkzeug.datastructures.FileStorage
        File sent by user.

    Returns
    -------
    str
        New filename based in md5 file hash.
    """
    hasher = hashlib.md5()
    basename = os.path.basename(file.filename)
    filename, extension = os.path.splitext(basename)
    file_read = file.read()
    hasher.update(file_read)
    processed_filename = hasher.hexdigest() + extension
    file.stream.seek(0)

    return processed_filename