Re: zope.testing.doctestunit pprint and deprecation warnings

On Thu, Dec 31, 2009 at 09:21:12AM +0800, Martin Aspeli wrote:
> Hanno Schlichting wrote:
> > On Wed, Dec 30, 2009 at 6:38 PM, Martijn Faassen<[email protected]>  wrote:
> >> zope.testing.doctestunit emits a deprecation warning. It also defines a
> >> function pprint. How does one use pprint without getting a deprecation
> >> warning? It seems impossible now, and an equivalent pprint doesn't
> >> appear to be in the standard library doctest..
> >
> > When I recently converted some tests, I replaced that pprint function
> > with the one from the standard library:
> >
> > from pprint import pprint
> >
> > There weren't any differences in the output, as far as I could tell.
> 
> Not sure if this is related, but one thing I found which bit me recently 
> is that prior to Python 2.5, pprint did not sort dict keys in the 
> output.

More precisely, it printed repr(dict) when the repr was shorter than the
number of columns pprint was aiming for.

> That means that a test like this:
> 
>   >>> pprint(foo)
>   {'omega': 1, 'alpha': 2}
> 
> will pass on 2.4 and fail on 2.5/2.6; to fix it for 2.5/2.6 you do:
> 
>   >>> pprint(foo)
>   {'alpha': 2, 'omega': 1}
> 
> but now it fails on 2.4.

Also, on 2.4 the dict order could change between 32 and 64-bit systems.

> The only way I could find it make it work 
> reliably was to not rely on dicts at all, but do:
> 
>   >>> pprint(sorted(foo.items())
>   [('alpha', 2), ('omega', 1)]
> 
> Which works the same on both. I don't know if the zope.doctest pprint 
> function was meant to fix this, but maybe it did?

Yes, by changing the default wrapping width of pprint.pprint() to 1
column, so it would force dict sorting (and add a bunch of extra newlines)

    >>> zope.testing.doctestunit.pprint(foo)
    {'alpha': 2,
     'omega': 1}

The extra newlines often got a bit ridiculous:

    >>> foo = {'alpha': [2, 3, 4, 5], 'omega': [1]}
    >>> zope.testing.doctestunit.pprint(foo)
    {'alpha': [2,
               3,
               4,
               5],
     'omega': [1]}

so I can't say I'll miss the doctestunit's pprint hack.

Marius Gedminas
-- 
http://pov.lt/ -- Zope 3 consulting and development

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