# Python Objects & Classes

### Creating object and classes \#

Python is an object-oriented language. In python everything is object i.e `int`, `str`, `bool` even modules, functions are also objects.

Object oriented programming use objects to create programs, and these objects stores data and behaviours.

### Defining class \#

Class name in python is preceded with `class` keyword followed by a colon (`:`). Classes commonly contains data field to store the data and methods for defining behaviors. Also every class in python contains a special method called *initializer* (also commonly known as constructors), which get invoked automatically every time new object is created.

Let's see an example.

Here we have created a class called `Person` which contains one data field called `name` and method `whoami()`.

### What is self? \#

All methods in python including some special methods like initializer have first parameter `self`. This parameter refers to the object which invokes the method. When you create new object the `self` parameter in the `__init__` method is automatically set to reference the object you have just created.

### Creating object from class \#

**Expected Output:**

**note:**

When you call a method you don't need to pass anything to `self` parameter, python automatically does that for you behind the scenes.

You can also change the `name` data field.

**Expected Output:**

Although it is a bad practice to give access to your data fields outside the class. We will discuss how to prevent this next.

### Hiding data fields \#

To hide data fields you need to define private data fields. In python you can create private data field using two leading underscores. You can also define a private method using two leading underscores.

Let's see an example

**Expected Output:**

Let's try to access `__balance` data field outside of class.

**Expected Output:**

AttributeError: 'BankAccount' object has no attribute '\_\_balance'

As you can see, now the `__balance` field is not accessible outside the class.

In next chapter we will learn about [operator overloading](https://chrome-extension/cjedbglnccaioiolemnfhjncicchinao/python-operator-overloading/).

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