Python Inheritance Calling Constructor Issue

Question

I have the following class inheritance structure:

class BuffEvent(object):
    def __init__(self, buffable):
        self.buffable = buffable


class BattleEvent(BuffEvent):
    def __init__(self, battle, buffable):
        super(BuffEvent, self).__init__(buffable)
        self.battle = battle


class BattleStartEvent(BattleEvent):
    def __init__(self, battle, buffable):
        super(BattleEvent, self).__init__(battle, buffable)

Then im tryng to call the constructor of BattleStartEvent like this:

BattleStartEvent(battle, battle.attacker)

But i am getting the following error:

    super(BattleEvent, self).__init__(battle, buffable)
TypeError: __init__() takes 2 positional arguments but 3 were given

In BattleStartEvent i have 2 parameters in the constructor so im a bit confused. What am i doing wrong here ?

The argument to super should be the class itself, not its super class. Or give no arguments at all, if you’re using a reasonably modern Python version. — deceze
– deceze ♦, Commented Aug 24, 2019 at 9:27

Tomerikoo · Accepted Answer · 2019-08-24 10:57:50Z

Your problem is not with the constructor of BattleStartEvent. It takes 2 arguments (aside from self), and that's what you are passing to it.

Your problem is then with the line inside said constructor:

super(BattleEvent, self).__init__(battle, buffable)

Doing super(BattleEvent, self) actually returns the class BuffEvent which takes one argument and as you can see you are passing 2 to it.

To fix this, either:

Fix your super() calls to use the actual class itself, not the parent (in all classes):

class BattleStartEvent(BattleEvent):
    def __init__(self, battle, buffable):
        super(BattleStartEvent, self).__init__(battle, buffable)

In Python 3: Call with "empty" super: super().__init__(battle, buffable)
I am guessing that this code is just for a reproducible example, but if your __init__ actually does nothing but call super, you can omit its implementation and the parent's __init__ will be called by default.

For more useful information about super, see Python’s super() considered super! by Raymond Hettinger.

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