Python: Passing self to class methods or arguments

Question

I am working on a python project with classes that have quite a few parameters and methods. In order to reduce complexity, I have been writing the methods as such:

def foo(self):
    return self.parameter1 * self.parameter2

Would it be better practice to explicitly pass the parameters?

def foo(self, parameter1, parameter2):
    return parameter1 * parameter2

This comes up because I have found it difficult to test the functions in the class without testing the entire class.

Answer 1

Your question makes some assumptions that are not consistent with OO design.

If parameter1 and parameter2 are not intrinsic properties of the object represented by self, then they need to be passed. If however, they are intrinsic properties of self, then they should have already been associated with self and do not need to be passed.

One major point of OO design, and objects in general, is to explicitly associate the data describing the object and the methods to work on the object together.

Answer:

Use a self reference for anything that is intrinsic to the object, and pass as a parameter those values which are not.

Answer 2

In order to reduce complexity, I have been writing the methods as such

The assumption of this purpose is wrong, self(instance variable) is supposed to be used if you define an instance method.

According to pylint: method_could_be_a_function: If a function could be run without self(instance variable), it should be an individual function, not an instance method.

For example:

class A(object):

    def __init__(self):
        self.some_instance_var

    def some_instance_method(self):
        #code here is suggested to be related to self(instance variable), eg:
        return self.some_instance_var

---

This one would be proper to put into class as an instance method.

class A(object):

    ...

    def foo(self):
        return self.parameter1 * self.parameter2

And this one should be a normal function, not an instance method. Because the content of function is not related to self(instance variable).

def foo(self, parameter1, parameter2):
    return parameter1 * parameter2