Classes are everywhere in Python. Even if you never define your own type of class, you will certainly use classes in Python.
>>> from point import Point >>> p = Point(1, 2, 3)
We can access the
x attribute? on this
Point object (aka
Point instance) or call the
is_origin method on it:
>>> p.x 1 >>> p.is_origin() False
When we check the
p (which is a
Point instance) it will tell us I am an object of type "class
>>> type(p) <class 'point.Point'>
The type of something is the same as the class of that thing.
Class instances (aka objects of some class/type) can have attributes and they can have methods.
We've seen attributes and methods in other places in Python too.
For example, lists have an
>>> numbers = [1, 2, 3] >>> numbers.append(4) >>> numbers [1, 2, 3, 4]
If you ask lists for their
type, you'll see some kind of class. You always get a class when you ask for the type of something in Python:
>>> type(numbers) <class 'list'>
The type of a list is the
list is not a function in Python, it's a class.
When you call
list with parentheses after it, you get an empty list back because we're constructing a new object) of type
>>> list() 
All the built-in data structures in Python are classes:
>>> tuple <class 'tuple'> >>> dict <class 'dict'> >>> set <class 'set'>
Interestingly, some of the even more fundamental types of objects are actually classes.
Anything that has a
type has a class.
When you ask for the type of a string you'll see
>>> name = "Trey" >>> type(name) <class 'str'>
We may have thought of
str as a function that can convert something to a string:
>>> str(4) '4'
But it's actually a class!
int is also a class:
>>> x = 4 >>> type(x) <class 'int'>
in fact, there are even attributes we can access on instances of the
>>> x.real 4 >>> x 4
We're accessing the
real attribute of object to get the real component of this number, which is the same as the number itself.
So, Integers are a class, which means if we call the
int function, we're actually calling a class to get back an integer instance:
>>> int('4') 4
A lot of the built-in functions in Python are actually classes too.
For example, when we call the
enumerate function, we'll get back an
>>> enumerate(numbers) <enumerate object at 0x7f58e8228c00>
enumerate "function" is actually a class:
>>> enumerate <class 'enumerate'>
It's not incorrect to say "the
enumerate function" even though
enumerate is implemented as a class because the distinction between classes and functions isn't very important in Python.
The distinction between classes and functions doesn't really matter that much in Python. The thing that I care about is the behavior: I care that I can call it.
When you call a function, we'll get the return value of that function. When you call a class, we'll get an instance of that class. Both functions and classes are callables and that's the thing we usually care about ("can I call it?").
So classes are everywhere in Python! Even if you never make your own class, you will certainly use classes.
Classes are a way to bundle functionality and state together.
The terms "type" and "class" are interchangeable:
bool are all classes.
You'll certainly use quite a few classes in Python (remember types are classes) but you may not need to create your own often.
Need to fill-in gaps in your Python skills? I send regular emails designed to do just that.
Sign up for my Python tips emails and I'll share my favorite Python insights with you every couple weeks.
Need to fill-in gaps in your Python skills? I send weekly emails designed to do just that.