On 9/11/2009 9:42 PM, Steven D'Aprano wrote:
However, I must admit I'm perplexed why the original example is calling
__unicode__() in the first place! Given the line:
raise self.severe('Problems with "%s" directive path:\n%s: %s.'
% (self.name, error.__class__.__name__, error))
it looks to me like it should be calling error.__str__() not
error.__unicode(). Making the suggested edit:
raise self.severe('Problems with "%s" directive path:\n%s: %s.'
% (self.name, error.__class__.__name__, str(error)))
should have no effect. But it (apparently) does. This brings us back to
Alan's original question:
"MYSTERY: how can "%s"%error be different from "%s"%str(error) in Python
2.6?"
George Brandl explained it to me this way:
It's probably best explained with a bit of code:
>>> >>> class C(object):
... def __str__(self): return '[str]'
... def __unicode__(self): return '[unicode]'
...
>>> "%s %s" % ('foo', C())
'foo [str]'
>>> "%s %s" % (u'foo', C())
u'foo [unicode]'
I.e., as soon as a Unicode element is interpolated into a string, further
interpolations automatically request Unicode via __unicode__, if it
exists.
Pretty subtle ...
Cheers,
Alan Isaac
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