Abstract classes are classes that contain one or more abstract methods.
By default, Python does not provide abstract classes.
Python comes with a module that provides the base for defining Abstract Base Classes (named ABC).
An abstract class can be considered as a blueprint for other classes.
By defining an abstract base class, you can define a common API for a set of subclasses.
A class that is derived from an abstract class cannot be instantiated unless all of its abstract methods are overridden.
[mythcat@desk ~]$ python3.9
Python 3.9.5 (default, May 4 2021, 00:00:00)
[GCC 10.3.1 20210422 (Red Hat 10.3.1-1)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from abc import ABC
>>> class Test_ABC(ABC):
... pass
...
>>> Test_ABC.register(tuple)
>>> assert issubclass(tuple,Test_ABC)
>>> assert isinstance((), Test_ABC)
>>> class Foo:
... def __getitem__(self, index):
... ...
... def __len__(self):
... ...
... def get_iterator(self):
... return iter(self)
...
>>> Test_ABC.register(Foo)
... Let's see an example:
from abc import ABC, abstractmethod
class Vehicle(ABC):
@abstractmethod
def action(self):
pass
class Air(Vehicle):
# overriding abstract method
def action(self):
print("this flies in the air")
class Ground(Vehicle):
# overriding abstract method
def action(self):
print("this running on the field")
class Civil(Ground):
def action(self):
print("Civil class - running on the field")
# Can't instantiate abstract class with abstract method action, don't use it
# abc = Vehicle()
abc = Air()
abc.action()
abc = Ground()
abc.action()
abc = Civil()
abc.action()
print( issubclass(Civil, Vehicle))
print( isinstance(Civil(), Vehicle))This is the result:
[mythcat@desk PythonProjects]$ python3.9 ABC_001.py
this flies in the air
this running on the field
Civil class - running on the field
True
True