Problem:
In hmac.py there's a type check that verifies that the msg parameter is of type bytes().

if not isinstance(msg, bytes):
    raise TypeError("expected bytes, but got %r" % type(msg).__name__)

That is incorrect. The hmac module should also work with other data types as long as they are supported by the underlying hashlib module, for example bytearray() and memoryview().

Suggestion:
Remove that type check. hashlib will make sure str() and other invalid data types raises a TypeError.

Good idea!

We can also lift the restriction for ``key`` a bit. It can also take a bytearray as argument. bytearray has translate() and supports bytes + bytearay.

Thanks for your patch! Please add tests for the new feature. The documentation needs versionchanged tags, too.

Patch updated to include tests and versionchanged tags

Thanks for your update.

As far as I can tell you haven't signed our contributor agreement yet. Can you please do so?

http://www.python.org/psf/contrib/
http://www.python.org/psf/contrib/contrib-form/

Of course. I've now signed and filed the agreement.

It may take a day or two until your signature makes it through red tape. I'll get back to you. :)

Your account hasn't been flagged yet. I'm going to ping the person in charge.

New changeset 636947fe131e by Christian Heimes in branch 'default':
Issue 18240: The HMAC module is no longer restricted to bytes and accepts
http://hg.python.org/cpython/rev/636947fe131e

Your CLA came through and I have applied your patch. Thank you very much for your contribution!