I want to understand arguments of the constructor __init__ in Python.
__init__
class Num: def __init__(self,num): self.n = num def getn(self)
The fact that your method does not use the self argument (which is a reference to the instance that the method is attached to) doesn't mean you can leave it out. It always has to be there, because Python is always going to try to pass it in.
self