Python __init__ Method In Inherited Class

I would like to give a daughter class some extra attributes without having to explicitly call a new method. So is there a way of giving the inherited class an __init__ type method

Solution 1:

As far as I know that's not possible, however you can call the init method of the superclass, like this:

class inheritedclass(initialclass):
    def __init__(self):
        initialclass.__init__(self)
        self.attr3 = 'three'

Solution 2:

Just call the parent's __init__ using super:

class inheritedclass(initialclass):
    def __new__(self):
        self.attr3 = 'three'
        super(initialclass, self).__init__()

I strongly advise to follow Python's naming conventions and start a class with a Capital letter, e.g. InheritedClass and InitialClass. This helps quickly distinguish classes from methods and variables.

Solution 3:

First of all you're mixing __init__ and __new__, they are different things. __new__ doesn't take instance (self) as argument, it takes class (cls). As for the main part of your question, what you have to do is use super to invoke superclass' __init__.

Your code should look like this:

class initialclass(object):
    def __init__(self):
        self.attr1 = 'one'
        self.attr2 = 'two'    

class inheritedclass(initialclass):
    def __init__(self):
        self.attr3 = 'three'
        super(inheritedclass, self).__init__()

Solution 4:

Just call a designated method from the parent's init, if it exists:

class initialclass():
    def __init__(self):
        self.attr1 = 'one'
        self.attr2 = 'two'  
        if hasattr(self, 'init_subclass'):
            self.init_subclass()

class inheritedclass(initialclass):
    def init_subclass(self):
        self.attr3 = 'three'

Solution 5:

class initialclass:
        def __init__(self):
                self.attr1 = 'one'
                self.attr2 = 'two'
class inheritedclass(initialclass):
        def __init__(self):
                super().__init__()
                self.attr3 = 'three'
        def somemethod(self):
                print (self.attr1, self.attr2, self.attr3)
a=inheritedclass()
a.somemethod()

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