No error while instantiating abstract class, even though abstract method is not implemented

Question

I was trying out the below python code:

from abc import ABCMeta, abstractmethod class Bar: __metaclass__ = ABCMeta @abstractmethod def foo(self): pass class Bar2(Bar): def foo2(self): print("Foo2") b = Bar() b2 = Bar2()

I thought having @abstractmethod will ensure that my parent class will be abstract and the child class would also be abstract as it is not implementing the abstract method. But here, I get no error trying to instantiate both the classes.

Can anyone explain why?

I did got exception b=Bar() TypeError: Can't instantiate abstract class Bar with abstract methods foo — Tanveer Alam
– Tanveer Alam, Commented Feb 24, 2015 at 5:50
@TanveerAlam Even I am surprised...I dont get the error...is it because of version? I am using 3.4 — codingsplash
– codingsplash, Commented Feb 24, 2015 at 5:52

nbro · Accepted Answer · 2017-02-14 00:40:50Z

7

You must set meta-class of Bar class to ABCMeta.

Python 2:

class Bar: __metaclass__ = ABCMeta @abstractmethod def foo(self): pass

Python 3:

class Bar(object, metaclass=ABCMeta): @abstractmethod def foo(self): pass

edited Feb 14, 2017 at 0:40

nbro

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answered Feb 24, 2015 at 5:43

M.javid

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1 Comment

Aleksandar Jovanovic Over a year ago

Additionally, there must be at least one abstract method in order for the error to be raised, like in your examples.

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