Walter Dörwald wrote:
__str__ and __unicode__ seem to behave differently. A __str__
overwrite in a str subclass is used when calling str(), a __unicode__
overwrite in a unicode subclass is *not* used when calling unicode():
-------------------------------
class str2(str):
def __str__(self):
return "foo"
x = str2("bar")
print str(x)
class unicode2(unicode):
def __unicode__(self):
return u"foo"
x = unicode2(u"bar")
print unicode(x)
-------------------------------
This outputs:
foo
bar
IMHO this should be fixed so that __unicode__() is used in the
second case too.
If you drop the base class for unicode, this already works.
This code in object.c:PyObject_Unicode() is responsible for
the sub-class version not doing what you'd expect:
if (PyUnicode_Check(v)) {
/* For a Unicode subtype that's not a Unicode object,
return a true Unicode object with the same data. */
return PyUnicode_FromUnicode(PyUnicode_AS_UNICODE(v),
PyUnicode_GET_SIZE(v));
}
So the question is whether conversion of a Unicode sub-type
to a true Unicode object should honor __unicode__ or not.
The same question can be asked for many other types, e.g.
floats (and __float__), integers (and __int__), etc.
>>> class float2(float):
... def __float__(self):
... return 3.141
...
>>> float(float2(1.23))
1.23
>>> class int2(int):
... def __int__(self):
... return 42
...
>>> int(int2(123))
123
I think we need general consensus on what the strategy
should be: honor these special hooks in conversions
to base types or not ?
Maybe the string case is the real problem ... :-)
--
Marc-Andre Lemburg
eGenix.com
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