{"id":425,"date":"2020-10-10T08:11:51","date_gmt":"2020-10-10T08:11:51","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=425"},"modified":"2025-03-31T07:05:55","modified_gmt":"2025-03-31T07:05:55","slug":"python-class","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/python-oop\/python-class\/","title":{"rendered":"Python Class"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn about Python classes and objects and how to define a new class.<\/p>\n\n\n\n

Objects #<\/a><\/h2>\n\n\n\n

An object is a container that contains data<\/strong> and functionality<\/strong>. <\/p>\n\n\n\n

The data<\/strong> represents the object at a particular moment in time. Therefore, the data of an object is called the state<\/strong>. Python uses attributes<\/strong> to model the state of an object.<\/p>\n\n\n\n

The functionality represents the behaviors<\/strong> of an object. Python uses functions<\/a> to model the behaviors. When a function is associated with an object, it becomes a method<\/strong> of the object.<\/p>\n\n\n\n

In other words, an object is a container that contains the state<\/strong> and methods<\/strong>. <\/p>\n\n\n\n

Before creating objects, you define a class first. And from the class, you can create one or more objects. The objects of a class are also called instances<\/strong> of a class. <\/p>\n\n\n\n

Define a class #<\/a><\/h2>\n\n\n\n

To define a class in Python, you use the class<\/code> keyword followed by the class name and a colon. The following example defines a Person<\/code> class:<\/p>\n\n\n

class<\/span> Person<\/span>:<\/span>\n    pass<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
By convention, you use capitalized names for classes in Python. If the class name contains multiple words, you use the CamelCase<\/code> format, for example SalesEmployee<\/code>.<\/p>\n\n\n\n
To create an instance of a class, you use the class name with parentheses like this:<\/p>\n\n\n
person = Person()<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
When printing out the person<\/code> object, you’ll see its name and memory address:<\/p>\n\n\n
class<\/span> Person<\/span>:<\/span>\n    pass<\/span>\n\nperson = Person()\nprint(person)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
<__main__.Person object at 0x000001C46D1C47F0<\/span>><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
To get an identity of an object, you use the id() function. For example:<\/p>\n\n\n
class<\/span> Person<\/span>:<\/span>\n    pass<\/span>\n\nperson = Person()\nprint(id(person))<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
1943155787760<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The id of an object is unique. In CPython, the id()<\/code> returns the memory address of an object. The hex()<\/code> function converts the integer returned by the id()<\/code> function to a lowercase hexadecimal string prefixed with 0x<\/code>:<\/p>\n\n\n
class<\/span> Person<\/span>:<\/span>\n    pass<\/span>\n\nperson = Person()\nprint(hex(id(person)))<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
0x1c46d1c47f0<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The person object is an instance of the Person<\/code> class. The isinstance()<\/code> function returns True<\/code> if an object is an instance of a class:<\/p>\n\n\n
class<\/span> Person<\/span>:<\/span>\n    pass<\/span>\n\nperson = Person()\n\nprint(isinstance(person, Person))  # True<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
True<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
A class is also an object in Python #<\/a><\/h2>\n\n\n\n
Everything in Python is an object, including classes.<\/p>\n\n\n\n
When you define the Person<\/code> class, Python creates an object with the name Person<\/code>. The Person<\/code> object has attributes. For example, you can find its name using the __name__<\/code> attribute:<\/p>\n\n\n
class<\/span> Person<\/span>:<\/span>\n    pass<\/span>\n\nprint(Person.__name__)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
Person<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The Person<\/code> object has the type of type<\/code>:<\/p>\n\n\n
class<\/span> Person<\/span>:<\/span>\n    pass<\/span>\n\nprint(type(Person))<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
<class<\/span> 'type<\/span>'><\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The Person<\/code> class also has a behavior. For example, it can create a new instance:<\/p>\n\n\n
class<\/span> Person<\/span>:<\/span>\n    pass<\/span>\n\nperson = Person()<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Since the Person<\/code> class is incomplete; you need to use the pass<\/a><\/code> statement to indicate that you’ll add more code to it later.<\/p>\n\n\n\n