Hi,
The problem is a side effect of the fact that old-style classes are
implemented on top of new-style meta-classes.
Consequently although C is the "class" of C() it is not its "type".
>>> type(C())
<type 'instance'>
>>> type(C()).__mro__
(<type 'instance'>, <type 'object'>)
therefore
>>> issubclass(type(C()), object)
True
which implies
>>> isinstance(C(),object)
True
Cheers,
Mark.
On 21/10/14 17:43, Andreas Maier wrote:
Hi. Today, I ran across this, in Python 2.7.6:
class C:
... pass
...
issubclass(C,object)
False
isinstance(C(),object)
True <-- ???
The description of isinstance() in Python 2.7 does not reveal this result
(to my reading).
From a duck-typing perspective, one would also not guess that an instance
of C would be considered an instance of object:
dir(C())
['__doc__', '__module__']
dir(object())
['__class__', '__delattr__', '__doc__', '__format__', '__getattribute__',
'__hash__', '__init__', '__new__', '__reduce__
', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__',
'__subclasshook__']
-> What is the motivation for isinstance(C,object) to return True in Python
2.7?
Andy
Andreas Maier
IBM Senior Technical Staff Member, Systems Management Architecture & Design
IBM Research & Development Laboratory Boeblingen, Germany
mai...@de.ibm.com, +49-7031-16-3654
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