{"id":172,"date":"2024-01-25T14:44:47","date_gmt":"2024-01-25T14:44:47","guid":{"rendered":"https:\/\/learnpython.elegantwallp.com\/?p=172"},"modified":"2024-01-25T14:44:49","modified_gmt":"2024-01-25T14:44:49","slug":"python-inheritance","status":"publish","type":"post","link":"https:\/\/learnpython.elegantwallp.com\/2024\/01\/25\/python-inheritance\/","title":{"rendered":"Python Inheritance"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you\u2019ll learn about Python inheritance and how to use the inheritance to reuse code from an existing class.<\/p>\n\n\n\n

Introduction to the Python inheritance<\/h2>\n\n\n\n

Inheritance allows a\u00a0class\u00a0to reuse the logic of an existing class. Suppose you have the following\u00a0Person<\/code>\u00a0class:<\/p>\n\n\n\n

class Person: def __init__(self, name): self.name = name def greet(self): return f\"Hi, it's {self.name}\"<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
The Person<\/code> class has the name<\/code> attribute and the greet()<\/code> method.<\/p>\n\n\n\n
Now, you want to define the\u00a0Employee<\/code>\u00a0that is similar to the\u00a0Person<\/code>\u00a0class:<\/p>\n\n\n\n
class Employee: def __init__(self, name, job_title): self.name = name self.job_title = job_title def greet(self): return f\"Hi, it's {self.name}\"<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
The Employee<\/code> class has two attributes name<\/code> and job_title<\/code>. It also has the greet()<\/code> method that is exactly the same as the greet()<\/code> method of the Person<\/code> class.<\/p>\n\n\n\n
To reuse the greet()<\/code> method from the Person<\/code> class in the Employee<\/code> class, you can create a relationship between the Person<\/code> and Employee<\/code> classes. To do it, you use inheritance so that the Employee<\/code> class inherits from the Person<\/code> class.<\/p>\n\n\n\n
The following redefines the\u00a0Employee<\/code>\u00a0class that inherits from the\u00a0Person<\/code>\u00a0class:<\/p>\n\n\n\n
class Employee(Person): def __init__(self, name, job_title): self.name = name self.job_title = job_title<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
By doing this, the Employee<\/code> class behaves the same as the Person<\/code> class without redefining the greet() method.<\/p>\n\n\n\n
This is a single inheritance<\/strong> because the Employee<\/code> inherits from a single class (Person<\/code>). Note that Python also supports multiple inheritances where a class inherits from multiple classes.<\/p>\n\n\n\n
Since the Employee<\/code> inherits attributes and methods of the Person<\/code> class, you can use the instance of the Employee class as if it were an instance of the Person<\/code> class.<\/p>\n\n\n\n
For example, the following creates a new instance of the\u00a0Employee<\/code>\u00a0class and call the\u00a0greet()<\/code>\u00a0method:<\/p>\n\n\n\n
employee = Employee('John', 'Python Developer') print(employee.greet())<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
Hi, it's John<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Inheritance terminology<\/h3>\n\n\n\n
The Person<\/code> class is the parent class<\/strong>, the base class<\/strong>, or the super class<\/strong> of the Employee<\/code> class. And the Employee<\/code> class is a child <\/strong>class, a derived class<\/strong>, or a subclass <\/strong>of the Person<\/code> class.<\/p>\n\n\n\n
The Employee<\/code> class derives from<\/strong>, extends<\/strong>, or subclasses <\/strong>the Person<\/code> class.<\/p>\n\n\n\n
The relationship between the Employee<\/code> class and Person<\/code> class is IS-A<\/strong> relationship. In other words, an employee is a<\/strong> person.<\/p>\n\n\n\n
type vs. isinstance<\/h2>\n\n\n\n
The following shows the type of instances of the\u00a0Person<\/code>\u00a0and\u00a0Employee<\/code>\u00a0classes:<\/p>\n\n\n\n
person = Person('Jane') print(type(person)) employee = Employee('John', 'Python Developer') print(type(employee))<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
<class '__main__.Person'> <class '__main__.Employee'><\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
To check if an object is an instance of a class, you use the\u00a0isinstance()<\/code>\u00a0method. For example:<\/p>\n\n\n\n
person = Person('Jane') print(isinstance(person, Person)) # True<\/em> employee = Employee('John', 'Python Developer') print(isinstance(employee, Person)) # True<\/em> print(isinstance(employee, Employee)) # True<\/em> print(isinstance(person, Employee)) # False<\/em><\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
True True True False<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
As clearly shown in the output:<\/p>\n\n\n\n
    \n
  • The person<\/code> is an instance of the Person<\/code> class.<\/li>\n\n\n\n
  • The employee<\/code> is an instance of the Employee<\/code> class. It\u2019s also an instance of the Person<\/code> class.<\/li>\n\n\n\n
  • The person<\/code> is not an instance of the Employee<\/code> class.<\/li>\n<\/ul>\n\n\n\n
    In practice, you\u2019ll often use the isinstance()<\/code> function to check whether an object has certain methods. Then, you\u2019ll call the methods of that object.<\/p>\n\n\n\n
    issubclass<\/h3>\n\n\n\n
    To check if a class is a subclass of another class, you use the\u00a0issubclass()<\/code>\u00a0function. For example:<\/p>\n\n\n\n
    print(issubclass(Employee, Person)) # True<\/em><\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    The following defines the\u00a0SalesEmployee<\/code>\u00a0class that inherits from the\u00a0Employee<\/code>\u00a0class:<\/p>\n\n\n\n
    class SalesEmployee(Employee): pass<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    The\u00a0SalesEmployee<\/code>\u00a0is the subclass of the\u00a0Employee<\/code>\u00a0class. It\u2019s also a subclass of the\u00a0Person<\/code>\u00a0class as shown in the following:<\/p>\n\n\n\n
    print(issubclass(SalesEmployee, Employee)) # True<\/em> print(issubclass(SalesEmployee, Person)) # True<\/em><\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    Note that when you define a class that doesn\u2019t inherit from any class, it\u2019ll implicitly inherit from the built-in object<\/code> class.<\/p>\n\n\n\n
    For example, the\u00a0Person<\/code>\u00a0class inherits from the\u00a0object<\/code>\u00a0class implicitly. Therefore, it is a subclass of the\u00a0object<\/code>\u00a0class:<\/p>\n\n\n\n
    print(issubclass(Person, object)) # True<\/em><\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    In other words, all classes are subclasses of the object<\/code> class.<\/p>\n","protected":false},"excerpt":{"rendered":"
    Summary: in this tutorial, you\u2019ll learn about Python inheritance and how to use the inheritance to reuse code from an existing class. Introduction to the Python inheritance Inheritance allows a\u00a0class\u00a0to reuse the logic of an existing class. Suppose you have the following\u00a0Person\u00a0class: The Person class has the name attribute and the greet() method. Now, you want to define the\u00a0Employee\u00a0that is similar […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[28],"tags":[],"class_list":["post-172","post","type-post","status-publish","format-standard","hentry","category-4-single-inheritance"],"_links":{"self":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/172","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/comments?post=172"}],"version-history":[{"count":1,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/172\/revisions"}],"predecessor-version":[{"id":173,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/172\/revisions\/173"}],"wp:attachment":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/media?parent=172"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/categories?post=172"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/tags?post=172"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}