CODEWITHSUNDEEP
pythonclasspython-2.7inheritance
pez
pez

Reputation: 4235

Python Class Inheritance: How to initialize a subclass with values not in the parent class

I'm trying to learn more about classes and OOP.

How can I have my Person class initialize with all the values of Entity but also with a value that may not be contained in the Entity class?

For example, both Person and Spirit inherit from Entity. However, only a Person would have a gender. How can I have Person initialize with gender as well?

After that, would I still be able to create an instance of Person and call describe() in the same way I've done below?

class Entity(object):

    def __init__(self, state, name, age):
        self.state = state
        self.name = name
        self.age = age

class Person(Entity):

    def describe(self):
        print "Identification: %s, %s, %s." % (self.state, self.name, self.age)

class Spirit(Entity):
    pass  # for now

steve = Person("human", "Steve", "23" # can I then list gender here?)
steve.describe()

Upvotes: 19

Views: 49301

Answers (2)

Tim Pozza
Tim Pozza

Reputation: 548

Transitionally, it looks like versions of Py 3.x (not sure which ones) allow this terse version of super():

def __init__(self, state, name, age, gender):
        self.gender = gender
        # Prototype initialization 3.x:
        super().__init__(state, name, age)

Been experimenting with SQLAlchemy models using dataclasses, so when I zipped on by looking at all things Python inheritance, I felt this might extend the answer: 

from dataclasses import dataclass

@dataclass
class Entity():
    state: str
    name: str
    age: int

@dataclass
class Person(Entity):
    gender: str

    def describe(self):
        print("State: {state}, Name: {name}, Age: {age}, Gender: {gender}"
            .format(state=self.state, name=self.name, age=self.age, gender=self.gender))

man = Person("human", "humanname", 21, "cisgendered")

man.describe()

Upvotes: 8

Matthew Trevor
Matthew Trevor

Reputation: 14962

Create a custom initializer on the sub-class and then call the parent class's initializer via super:

class Person(Entity):
    def __init__(self, state, name, age, gender):
        self.gender = gender
        super(Person, self).__init__(state, name, age)

Upvotes: 32

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