On 11/29/2012 9:59 AM, lars van gemerden wrote:
Hi,
I have encountered some strange behavior of isinstance(/issubclass): depending
on the import path used for classes i get different output, while the classes i
compare are in the same file.
Basically if i import a class as:
from mod1.mod2 import A
or:
from mod0.mod1.mod2 import A
which both result in importing the same class,
As other said, both import the same abstract class but create two
different concrete class objects.
> a call to isinstance(inst, A) in another module can have a different
output.
In this module
print type(inst), A, isinstance(inst, A), issubclass(type(inst), A)
gives:
<class 'mod0.mod1.mod2.A'> <class 'mod1.mod2.A'> False False
Add print id(type(inst)), id(A) and you will see that they are different
objects. The isinstance and issubclass calls compare the classes by
identity (the default meaning of ==) and so False, False are correct.
--
Terry Jan Reedy
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