How can I add attributes to a derivated class?

Question

class Human():
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def hablar(self, message):
        print(message)


class Alien(Human):
    def __init__(self, planet):
        self.planet = planet

    def fly(self):
        print("I'm flying!")

This code is an example to show what I want to do. Imagine that I want an alien to inheritance all the properties of a Human but I also want him to have a planet attribute to distinguish from which planet does it comes.

When I do it as I did it in the mentioned code, it didn't work. Is it possible to do it? How?

Thanks!

Raphaele Adjerad · Accepted Answer · 2020-04-23T06:02:15.723

1

You might want to refer to this question about calling parent class constructor from a child class.

You need to use the dunder method __init__ of the parent class inside the __init__ of Alien as so:

class Human():
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def hablar(self, message):
        print(str(message))


class Alien(Human):

    def __init__(self, name, age, planet):
        super().__init__(name, age)
        self.planet = planet

    def fly(self):
        print("I'm flying!")

edited Apr 23 '20 at 06:02

answered Apr 23 '20 at 05:57

Raphaele Adjerad

1,117
6
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Refer here please https://stackoverflow.com/questions/12557612/calling-a-parent-class-constructor-from-a-child-class-in-python – rajeshkumargp Apr 23 '20 at 06:02
Like so `alien = Alien("ET", "99", "Somewhere")` for instance. – Raphaele Adjerad Apr 23 '20 at 06:08
Should the super class constructor be called before the base class variables are assigned or the other way around? What's the convention? – Judy T Raj Mar 05 '21 at 11:58

score 1 · Answer 2 · answered Apr 23 '20 at 05:58

1

You need to reference the constructor of the parent class.

class Alien(Human):
    def __init__(self, name, age, planet):
        super().__init__(name, age)
        self.planet = planet

answered Apr 23 '20 at 05:58

Jake Tae

1,681
1
8
11

score 1 · Answer 3 · answered Apr 23 '20 at 06:10

class Human():
    def __init__(self, name, age):
        self.name = name 
        self.age = age

class Alien(Human):
    def __init__(self, planet, **kwargs):
        self.planet = planet
        super(Alien, self).__init__(**kwargs)


Z = Alien(planet='Venus',name='Z',age=21)
print(Z.__dict__)

output:

{'planet': 'Venus', 'name': 'Z', 'age': 21}

How can I add attributes to a derivated class?

3 Answers3