To **define a class** you first need to know why it's necessary for object-oriented programming. When working on complex programs, in particular, *object-oriented* programming lets you reuse code and write code that is more readable, which in turn makes it more maintainable.

# What are classes?

A class is a **user-defined** data type which includes local *methods* and *properties*.

Classes are an important concept in *object-oriented* programming.

One of the big differences between *functions* and *classes* is that a class contains both *data* (variables) called **properties**  and **methods** (*functions* defined inside a *class*). 



# Syntax

The syntax for defining a *class* is as follows:

# Example
Now let's define a class named `Shape`:

class Shape:
  sides = 4 #first property
  name = "Square" #second property
  def description(a): #method defined
    return ("A square with 4 sides")
    
s1 = Shape() #creating an object of Shape
print "Name of shape is:",(s1.name)
print "Number of sides are:",(s1.sides)
print s1.description()

## Explanation

The class `Shape` has the following properties:

* `sides`
* `name`

and the following method:

* `description`

You might have noticed that the *argument* passed to the *method* is the word `self`, which is a *reference* to objects that are made based on this class. To reference the instance of the class, `self` will always be the *first* parameter.

How to define classes in Python

Classes in Python organize code for readability and reusability in object-oriented programming, combining data and methods.