Making a type of your own

Not everything fits into an int, a str or a list. A class is a custom type you define yourself, bundling related values — and later, functions — into one thing.

You start one with the class keyword, a name, and a colon:

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

__init__ — short for initialize, with two underscores each side — runs every time you make one. Its job is to set up the attributes: the values this particular instance will carry around.

self is the instance being worked on. Every method takes it as its first parameter, and self.name = name means "store this argument on this object". It is a quirk of Python that you write it out; you get used to it.

To create one, call the class by name — the arguments go to __init__, and you never pass self yourself:

p = Person("Ada", 36)
p.name      # "Ada"

Define a class Person whose __init__ takes name and age and stores both.

Then create two of them:

• p1 — Toby, aged 16
• p2 — Dumbledore, aged 115