[Python-Dev] Issue 3745 backwards incompatibility

M.-A. Lemburg mal at egenix.com
Tue Dec 15 12:23:12 CET 2009

Karen Tracey wrote:
> In testing some existing code with the 2.7 alpha release, I've run into:
>     TypeError: Unicode-objects must be encoded before hashing
> when the existing code tries to pass unicode objects to hashlib.sha1 and
> hashlib.md5.  This is, I believe, due to changes made for issue 3745:
> http://bugs.python.org/issue3745
> The issue states the need to reject unencoded strings based on the fact that
> one backend implementation (openssl) refused to accept them while another
> (_sha256) assumed a utf-8 encoding.  The thing is, I cannot observe any such
> difference using Python 2.5 or 2.6.  Instead of what is shown in the ticket
> (which was done on a Python 3, I believe) I see, when I adjust the demo test
> to use Python 2 syntax for "unencoded strings":

I think this was a misunderstanding during the issue 3745 processing:
the patch should not have been backported to trunk at all.

For Python 3.x, the change was correct. For 2.x, a -3 warning
would have been a better fit.

Note that the non-OpenSSL SHA et al. modules have never defaulted to
encoding to UTF-8 in Python 2.x. Python 2.x uses ASCII as default
encoding. Only Python 3.x uses UTF-8 as default encoding.

I've added a note to the issue and reopened it.

Marc-Andre Lemburg

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