But METH_O makes the update method does not work.

>>> _sha1.sha1().update(b'a')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
SystemError: new style getargs format but argument is not a tuple

But if you change METH_O to METH_VARARGS, it works again. I'll chip Christian Heimes. Maybe he has something to say about this.

Other than that, I need to update my patch because currently with my patch, the sha1 constructor accepts None value. The default behaviour is to reject None value. So I need to use advanced feature of clinic for this purpose.

I think I can convert all sha modules (including md5) in this weekend. However, _codecsmodule is totally different beast. 43 sites.... >.<