Python child class initialiser argument

Question

I have a parent class whose initialiser has three argument, now I want to have a child class whose initialiser only has two argument, but it's telling me it has to be given three arguments when I try to create the child object.

class Parent(Exception):
 def _init_(self, a, b):
 ...
 super(Parent, self)._init_(a, b)
class Child(Parent):
 def _init_(self, b):
 super(Child, self)._init_(123, b)
# somewhere in the code I have:
raise Child("BAD_INPUT")

What I'm trying to do is instantiate a Child object with only one argument then in the initialiser of that Child object call Parent's initialiser and pass in two argument, one is hard-coded (123) .

Error I got: TypeError: __init__() takes exactly 3 arguments (2 given)

• Moses Koledoye: _init_ -> __init__?
• Michel Touw: When I run this code and fix the indent on super(Parent, self)._init_(a, b) I get no exception, except for the one you raise
• Arch1tect: OMG!!! I wasted hours on this, __ is really the problem!! Python should give me a better error message.. T T
• Yaroslav Nikitenko: Maybe you remove your question in that case? The title is very misleading. "Python child class initialiser argument" I think there is no use to save code with typos.

Answer 1

you should be able to use:

class Parent(Exception):
 def __init__(self, a, b):
 self.a = a
 self.b = b
class Child(Parent):
 a = 123
 def __init__(self, b):
 super().__init__(self.a, b)

• Moses Koledoye: There is no such thing as __super__. And the problem is with the _init_ missing extra underscores which your answer does not solve