Question

i have a class that will make multiple instances. whats the difference between making a method and calling that method versus making a class and a function then using that function on the class? Does the first cost more memory because the method is “instantiated”?

Example:

class myclass:
    def __init__(self):
        self.a=0

    def mymethod:
        print self.a

inst1=myclass()
myclass.mymethod

versus:

class myclass:
    def __init__(self):
        self.a=0

def myfunction(instance):
    print instance.a

inst1=myclass()
myfunction(inst1)

Answer 1

Methods are really just functions that always receive a class instance as a first parameter (and happen to be declared within the scope of a class). The code of a method is shared across all instances, so you won’t be “instantiating” a method every time you make a class instance.

So, they are really equivalent; you use whatever is the clearest expression of your intent (readability counts!). If you are writing a function that always takes an instance of a specific class as an argument, it is probably clearest expressed as a method. If the function can operate on many different kinds of classes, it may be clearest as a function.