How to Call a method of class having no argument

[buran]

Is it necessary to have all the class methods should have at least 1 argument (self) in our case

all instance and class methods should have one argument. For instance methods, by convention, we call that argument self. For class methods we use, again by convention, cls.
And there are staticmethods that answer to your next question:

Can't we have no arguments ?

As ichabood explained you need to declare it staticmethod. However in this case the question is does it really belong to a class or can simply be a function, outside class. i.e. if it doesn't need to access instance or the class

Google the difference between instance, class, static methods and simple function