On 3/4/2010 11:11 PM, "Martin v. Löwis" wrote:
Johan Harjano ran into an interesting problem when trying to run the
Django test suite under Python 3.1.
Django has doctests of the form
a6.headline
u'Default headline'
Even when converting the doctest with 2to3, the expected output is
unmodified. However, in 3.x, the expected output will change (i.e. not
produce an u"" prefix anymore).
Now, it might be possible to reformulate the test case (e.g. use print()
instead of relying on repr), however, this is undesirable as a) the test
should continue to test in 2.x that the result object is a unicode
string, and b) it makes the test less readable.
I would like to find a solution where this gets automatically corrected,
e.g. through 2to3, or through changes to doctest, or through changes of
str.__repr__.
Any proposal appreciated.
What is the easiest thing that works?
If 2to3 can fix string literals and fix code within doc strings, would
it be difficult to fix expected strings within doc strings?
On the otherhand, as Foord pointed out, the 'u' prefix is something of a
CPythonism not required by the language def, so an 'ignore leading u on
expected output' flag would be useful. But 'correcting'
>>> a,b
u'ah', u'hah'
is too much to expect. Doctest is both useful and fragile because it
*almost* imitates human testing methods.
If tests like the above were bunched, and my primary goal were to make
Django tests work, and work now, without changing the style, I would be
tempted to use something like the following:
def u(s): #import as needed from a testutil module
if type(s) is unicode: # str in 3.x
print(s)
else print('') #or any 'nevermatch' string
>>> u(a6.headline)
'Default headline'
which both retains the type test and readability. This would be a
project specific solution, but then, the other comments suggest that
wanting to combine a type and value test this way seems to be someone
project specific.
Terry Jan Reedy
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