all Python 3abcfunction

abc.abstractmethod

abstract classes

A decorator marking a method abstract; subclasses must override it.

Syntax

@abc.abstractmethod

The decorator enforces nothing on its own — it just sets the __isabstractmethod__ flag on the function; refusing instantiation is the job of the ABCMeta metaclass. In a class that uses neither ABC nor ABCMeta the mark is silently ignored and the "abstract" method stays perfectly callable. When stacking decorators, abstractmethod must be the innermost one, with @classmethod or @property sitting above it.

Examples

import abc
class B(abc.ABC):
    @abc.abstractmethod
    def f(self): ...
print('f' in B.__abstractmethods__)   # → True

See also

Common errors

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