{"id":473,"date":"2020-10-12T11:35:20","date_gmt":"2020-10-12T11:35:20","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=473"},"modified":"2025-03-31T10:09:17","modified_gmt":"2025-03-31T10:09:17","slug":"python-properties","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/python-oop\/python-properties\/","title":{"rendered":"Python Property"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn about the Python property<\/code> class and how to use it to define properties for a class.<\/p>\n\n\n\n

Introduction to class properties #<\/a><\/h2>\n\n\n\n

The following defines a Person<\/code> class<\/a> that has two attributes<\/a> name<\/code> and age<\/code>, and create a new instance of the Person<\/code> class:<\/p>\n\n\n

class<\/span> Person<\/span>:<\/span>\n    def<\/span> __init__<\/span>(self, name, age)<\/span>:<\/span>\n        self.name = name\n        self.age = age\n\n\njohn = Person('John'<\/span>, 18<\/span>)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
john.age = 19<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The following assignment is also technically valid:<\/p>\n\n\n
john.age = -1<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
However, the age is semantically incorrect. <\/p>\n\n\n\n
age = -1<\/span>\nif<\/span> age <= 0<\/span>:\n    raise<\/span> ValueError('The age must be positive'<\/span>)\nelse<\/span>:\n    john.age = age<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
And you need to do this every time you want to assign a value to the age<\/code> attribute. This is repetitive and difficult to maintain.<\/p>\n\n\n\n
To avoid this repetition, you can define a pair of methods called getter and setter.<\/p>\n\n\n\n
Getter and setter #<\/a><\/h2>\n\n\n\n
The getter and setter methods provide an interface for accessing an instance attribute:<\/p>\n\n\n\n
To ensure that the age is not zero or negative, you use the if<\/a><\/code> statement to add a check as follows:<\/p>\n\n\n
Since age<\/code> is the instance attribute<\/a> of the Person<\/code> class, you can assign it a new value like this:<\/p>\n\n\n