Self. What is it, why do I care?
19 May 2018Happy Saturday! Let’s talk about self. No, not me, your self - nevermind.
Why is the self argument required in a method, and what good does it do me? First, some context. My program has a menu class for users to make a selection:
print(“1) Thing 1” + “\n 2) Thing 2” + “\n 3) Thing 3”) choice = input(“Select one:”) build(choice)
The user enters a number, and the module then calls this class’ method build(). When build() is called, however, Python returns:
build() takes 1 positional argument but 2 were given
What gives? We only included one argument.
Well, kind of. We included only one explicit argument. That’s not all that’s going on here. Methods by definition include an implicit self argument when called, in addition to what’s explicitly passed. build() always passes the self argument at minimum. Behind the scenes, build(choice) really looks like (and remember, “object” is the instance of our class here)
Class.build(object, choice)
Two arguements! This “object” is usually refered to as self. So why do we care? This is great: Self represents a class instance from inside itself. That means we have convienent access to an instance’s attributes and methods from inside the build() method. Anything my Object has as an attribute, build() can use with the syntax self.attribute, or methods with self.method().