Prototype Design Pattern in Python...

title: Prototype Design Pattern in Python... date: '2000-01-01' tags:

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The prototype design pattern is a creational pattern.

If the creation of an object is a very costly affair and we already have a similar kind of object, instead of creating it each time we need it, we use the clone of the object that is already there.

Suppose, there is a large object with many attributes whose data we read from a database. We need to modify that data multiple times in our program. So instead of creating the object each time by reading from the database, we tend to keep a prototype object - we clone it, and then work on it.

In Python, there is a module called copy which has two methods - copy() and deepcopy(). The first one is for the shallow copy and the second one is for the deepcopy.

Here is the source code of an example of the Prototype design pattern.

from abc import ABC, abstractmethod
import copy

class Person(ABC):
    def __init__(self, name):
        self._name = name

    def set_name(self, name):
        self._name = name

    def get_name(self):
        return self._name

    @abstractmethod
    def clone(self):
        pass

    @abstractmethod
    def display(self):
        pass

class Teacher(Person):
    def __init__(self, name, course):
        super().__init__(name)
        self._course = course

    def set_course(self, course):
        self._course = course

    def get_course(self):
        return self._course

    def display(self):
        print("\nTeacher's name: ", self._name)
        print("He teaches: ", self.get_course())

    def clone(self):
        return copy.deepcopy(self)

class Student(Person):
    def __init__(self, name, teacher):
        super().__init__(name)
        self._teacher = teacher

    def display(self):
        print("\nStudent's name: ", self.get_name())
        print("Taught by: ", self._teacher.get_name())
        print("Enrolled in the subject: ", self._teacher.get_course())

    def clone(self):
        return copy.deepcopy(self)

if __name__ == '__main__':
    teacher = Teacher('Som', "Python Design Pattern")
    teacherClone1 = teacher.clone()

    student = Student("Ridit", teacherClone1)
    studentClone1 = student.clone()

    teacherClone1.set_course("DSA")

    teacherClone1.display()
    studentClone1.display()

If we run the above piece of code the result will be as follows:

Teacher's name : Som

He teaches : Python Design Patttern

Teacher's name : Som

He teaches : DSA

Student's name : Ridit

Taught by : Som

Enrolled in the subject : Python Design Patttern

As you can see, we have used deep copy here.