I am currently learning the Template Method pattern in python.
I am wondering if there is any way to protect some of the functions from the base class so that the subclass cannot overwrite? As below, the _primitive_operation_3
from the subclass overwrites the same function from the base class.
import abc
class AbstractClass(metaclass=abc.ABCMeta):
"""
Define abstract primitive operations that concrete subclasses define
to implement steps of an algorithm.
Implement a template method defining the skeleton of an algorithm.
The template method calls primitive operations as well as operations
defined in AbstractClass or those of other objects.
"""
def template_method(self):
self._primitive_operation_1()
self._primitive_operation_2()
self._primitive_operation_3()
# Functions must be specified by subclass (i.e., subclass variant)
@abc.abstractmethod
def _primitive_operation_1(self):
pass
# Functions must be specified by subclass (i.e., subclass variant)
@abc.abstractmethod
def _primitive_operation_2(self):
pass
# Functions inherited and not modified by subclass (i.e., subclass invariant)
def _primitive_operation_3(self):
print ('Execute operation #3 from main class')
class ConcreteClass(AbstractClass):
"""
Implement the primitive operations to carry out
subclass-specificsteps of the algorithm.
"""
def _primitive_operation_1(self):
pass
def _primitive_operation_2(self):
pass
# You can still overwrite it if you want
def _primitive_operation_3(self):
print ('Execute operation #3 from subclass')
def main():
concrete_class = ConcreteClass()
concrete_class.template_method()
if __name__ == "__main__":
main()
Aucun commentaire:
Enregistrer un commentaire