Why to use __setattr__ in python?

Question

I don\'t know for why using __setattr__ instead simple referencing like x.a=1.

I understand this example:

class Rectangle:         


        

Answer 1

__setattr__ is a class method that is called by setattr builtin method. That is, if __setattr__ is defined in given class. Most often you do not declare your own version of __setattr__ so I assume you are asking of what use is the setattr method.

Suppose you have a var with the name of the attribute you want to set instead of just knowing the name:

class A(object):
    def doSth(self, name, val):
        setattr(self, name, val)

impossible to do with self.name = val

Also, a common usage is with keyword args:

class A(object):
    def __init__(self, *args, **kwargs):
        for k,v in kwargs.items():
            setattr(self, k, v)