Python may not call the __instancecheck__ method.
Running the following code
It should be False → True
It should be False→ False
It should be False→ False
It should be False→ False
appears.
Actually, the first one should show False, but it says True.
Why isn't it called?
Thank you for your cooperation.
class Analysis (type):
def__instancecheck__(self, other):
return False
class SMA (metacclass=Analysis):
pass
sma = SMA()
print('It should be False→', isinstance(sma,SMA))
print('It should be False→', isinstance(1,SMA))
print('It should be False→', isinstance([], SMA))
print('It should be False→', isinstance(', SMA))
Reprinted from argus' comment.
The source code does not run __instancecheck__ because it first performs a type check and immediately returns True if the object is an instance of the specified class.Here, since sma is an instance of the SMA class, it returns True and ends.
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