[Python-Dev] doctest, unicode repr, and 2to3 (original) (raw)

Michael Foord fuzzyman at voidspace.org.uk
Fri Mar 5 17:11:59 CET 2010

On 05/03/2010 15:56, Antoine Pitrou wrote:

Le Thu, 4 Mar 2010 23:30:12 -0500, Barry Warsaw<barry at python.org> a écrit :

If you really want to test that it's a unicode, shouldn't you actually test its type? (I'm not sure what would happen with that under 2to3.) Besides, the type of the string is very rarely important, so I think the u-prefix and quotes is mostly just noise. String type is actually very important, if you don't want your application/library to fail in the face of non-ASCII data. That's why we did all this thing in py3k, after all :)

Well, I'd like to see a 'unicode agnostic' mode for different reasons - although given that it all changes in Python 3 and it is almost certainly too late to get changes to doctest before the 2.7 release the point is probably moot.

IronPython has very different unicode behaviour to Python 2. IronPython is like Python 3 in this regard, all strings are unicode (str is unicode). This means that it rarely puts the u prefix on strings. So doctests that use string repr also fail on IronPython - the django doctest suite is a culprit in this regard too.

Dictionary iteration order is also different in IronPython - so dict reprs also fail. For dict reprs it would be nice if doctest compared in an order agnostic way. (Internally reconstruct the dict as a dict of strings from the repr and then compare using dict equality.)

I know it is easily possible to construct doctests that are robust against these differences, but the fact that the "obvious-thing" often fails in subtle ways on other platforms are one of the reasons I don't consider doctest to be a suitable tool for unit testing [1]. :-)

Michael

[1] It isn't the main reason and I realise that is entirely orthoganal anway... but doctest makes every line an assertion, and you have to jump through hoops if you don't want that behaviour. All besides the point. Doctest simply rocks for testing documentation examples - especially in conjunction with Sphinx.

Regards

Antoine.

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