![\"classes](\"https:\/\/techvidvan.com\/tutorials\/wp-content\/uploads\/sites\/2\/2020\/01\/python-classes.jpg\")
<\/a><\/h3>\nPython<\/strong> is an object-oriented language<\/strong> and everything in it is an object<\/strong>. By using Python classes<\/strong> and objects<\/strong>, we can model<\/strong> the real world<\/strong>.<\/p>\n A class<\/strong> is like a blueprint<\/strong> for objects<\/strong> – it has no values<\/strong> itself. It is an abstract data type<\/strong>. We can have multiple objects<\/strong> of one class<\/strong>.<\/p>\n To define a class<\/strong>, we use the class keyword<\/strong>, not<\/strong> the def keyword<\/strong> we used to define functions<\/strong>.<\/p>\n Let\u2019s take an example<\/strong>.<\/p>\n Code:<\/strong><\/p>\n This was an empty class<\/strong>.<\/p>\n Now let\u2019s declare a variable<\/strong> in it.<\/p>\n Code:<\/strong><\/p>\n This is a class Fruit<\/strong>.<\/p>\n We use PascalCase<\/strong> to name classes<\/strong> here. And because Python does not<\/strong> use curly braces<\/strong>, you need to indent<\/strong> the block of code<\/strong> in the class<\/strong>. Without that, it will raise <\/strong>an exception<\/strong>.<\/p>\n There is no<\/strong> need to use<\/strong> the new keyword<\/strong> for creating<\/strong> objects in Python<\/strong>. Just use this class constructor<\/strong>:<\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n This calls the __init__()<\/strong> method in the Fruit class<\/strong>.<\/p>\n We did not<\/strong> declare it, but it uses the default one<\/strong>.<\/p>\n Python classes<\/strong> can also have docstrings<\/strong> to explain what they do. But if you add<\/strong> a docstring<\/strong> to a class, it should be the first thing<\/strong> in the class<\/strong>.<\/p>\n Code:<\/strong><\/p>\n Code:<\/strong><\/p>\n So what is __init__()<\/strong>?<\/p>\n In most cases, we will need the __init__() method for classes<\/strong>.<\/p>\n This is a magic method (dunder method)<\/strong> which we can use to initialize values<\/strong> for classes (objects)<\/strong>. So __init__() has initialization code<\/strong>.<\/p>\n Every class<\/strong> has __init__<\/strong> and this is executed<\/strong> when we instantiate<\/strong> the class<\/strong>. You can also use this method to do anything<\/strong> you want to do when the object<\/strong> is being created<\/strong>.<\/p>\n Let\u2019s learn with an example.<\/p>\n Code:<\/strong><\/p>\n We have created<\/strong> the class<\/strong>, now let\u2019s learn to create an object<\/strong> for it and access<\/strong> its values<\/strong>.<\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n Here, class Fruit has an object orange<\/strong>. This has a name<\/strong>, color<\/strong>, and size<\/strong>.<\/p>\n The name for all fruits is name<\/strong>, and color<\/strong> and size<\/strong> are passed as arguments<\/strong>. So orange<\/strong> is the object with color \u2018orange\u2019<\/strong> and size 8<\/strong>. We accessed<\/strong> the values<\/strong> with the dot operator<\/strong>.<\/p>\n We will talk about the \u2018self\u2019 parameter<\/strong> in the next section.<\/p>\n Python classes can have both methods and functions. Functions are standalone and not associated with an object. However, methods are functions that belong to an object and can modify its state. Each method in a class must take the self parameter as the first parameter. This parameter refers to the instance of the class, allowing the method to access and modify the object\u2019s attributes. You can name this parameter anything you like, but by convention, it is always named self.<\/p>\n Let\u2019s define a method in class Fruit<\/strong>.<\/p>\n Code:<\/strong><\/p>\n Code:<\/strong><\/p>\n Now, we can call the show()<\/strong> method on the orange object<\/strong>. For this, we use the dot operator<\/strong>.<\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n You can call the self parameter<\/strong> anything.<\/p>\n Code:<\/strong><\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n You also have to use<\/strong> the self parameter<\/strong> even when a method does not<\/strong> take any parameters<\/strong>.<\/p>\n In Python classes, we use the dot operator<\/strong> to access object<\/strong> properties<\/strong> and methods<\/strong>, but we can also use it to modify them<\/strong>.<\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n And we can also delete<\/strong> them with the del keyword<\/strong>.<\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n We can also delete<\/strong> the complete<\/strong> object with the del keyword<\/strong>.<\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n The Python Classes create<\/strong> new local<\/strong> namespaces<\/strong> with their attributes (data or functions)<\/strong>. You can make a variable<\/strong> belong to a class<\/strong>. This is not<\/strong> like instance variables<\/strong> which belong to objects<\/strong>.<\/p>\n Code:<\/strong><\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n Here, the class Fruit<\/strong> has the class variable<\/strong> \u2018orange\u2019, but the orange object<\/strong> also has it.<\/p>\n Python<\/strong> has some built-in class attributes<\/strong> that we can use to get more information<\/strong> about the class<\/strong>.<\/p>\n a. __dict__ –<\/strong> It is a dictionary<\/strong> consisting of the class\u2019 namespace<\/strong>.<\/p>\n Code:<\/strong><\/p>\n Output:<\/strong><\/p>\n b. __doc__ –<\/strong> It is the class docstring<\/strong>, but is None<\/strong> if there is no docstring<\/strong> in the class<\/strong>.<\/p>\nDefining a Class in Python<\/h3>\n
>>> class Fruit:\r\n pass<\/pre>\n
>>> class Fruit:\r\n name=\u2019fruit\u2019<\/pre>\n
Creating an Object in Python<\/h3>\n
>>> orange=Fruit()\r\n>>> orange.name<\/pre>\n
>>> class MyClass:\r\n '''This class does nothing'''\r\n pass<\/pre>\n
>>> MyClass\r\n<class '__main__.MyClass'><\/pre>\n
The __init__() Method<\/h3>\n
>>> class Fruit:\r\n def __init__(self, color, size):\r\n self.name='fruit'\r\n self.color=color\r\n self.size=size<\/pre>\n
1. Accessing Values<\/h4>\n
>>> orange=Fruit('orange',8)\r\n>>> orange.name<\/pre>\n>>> orange.color<\/pre>\n
>>> orange.size<\/pre>\n
Python Classes Methods<\/h3>\n
>>> class Fruit:\r\n def __init__(self, color, size):\r\n self.name='fruit'\r\n self.color=color\r\n self.size=size\r\n def show(self):\r\n print(f'I am a {self.name}, I am {self.color} and of size {self.size}')<\/pre>\n>>> orange=Fruit('orange',8)<\/pre>\n>>> orange.show()<\/pre>\n
>>> class Fruit:\r\n def __init__(obj, color, size):\r\n obj.name='fruit'\r\n obj.color=color\r\n obj.size=size\r\n def show(obj):\r\n print(f'I am a {obj.name}, I am {obj.color} and of size {obj.size}')<\/pre>\n>>> orange=Fruit('orange',8)\r\n>>> orange.show()<\/pre>\nChanging Object Properties<\/h3>\n
>>> orange.size=9\r\n>>> orange.size<\/pre>\n
>>> del orange.size\r\n>>> orange.size<\/pre>\n
\n\u00a0\u00a0<\/b>File “<pyshell#33>”, line 1, in <module>
\n\u00a0\u00a0\u00a0\u00a0<\/b>orange.size
\nAttributeError: ‘Fruit’ object has no attribute ‘size’<\/div>\n>>> del orange\r\n>>> orange.size<\/pre>\n
\n\u00a0\u00a0<\/span>File “<pyshell#35>”, line 1, in <module>
\n\u00a0\u00a0\u00a0\u00a0<\/span>orange.size
\nNameError: name ‘orange’ is not defined<\/div>\nPython Class Variables<\/h3>\n
>>> class Fruit:\r\n name='fruit'\r\n def __init__(obj, color, size):\r\n obj.color=color\r\n obj.size=size\r\n def show(obj):\r\n print(f'I am a {obj.name}, I am {obj.color} and of size {obj.size}')<\/pre>\n>>> orange=Fruit('orange',8)\r\n>>> orange.name<\/pre>\n1. Built-in Class Attributes<\/h4>\n
>>> Fruit.__dict__<\/pre>\n