Python Tutorials
Tags: ,
Categories: ,

Overview

Python inheritance allows a class (child class) to inherit all the methods and properties from another class (parent class).

Creating a Parent Class

Any class can become a parent class, so the syntax is the same as creating any other class.

class Person:
    def __init__(self, fname, lname):
        self.firstname = fname
        self.lastname = lname

    def printname(self):
        print(self.firstname, self.lastname)

x = Person("Johnny", "Shay")
x.printname()

Output:

Johnny Shay

Creating a Child Class

The child class can have new methods and properties, but will also inherit those of the parent class.

class Person: #parent class
    def __init__(self, fname, lname):
        self.firstname = fname
        self.lastname = lname

    def printname(self):
        print(self.firstname, self.lastname)

class Student(Person): #child class
    pass #because the class is created empty except for the inheritance

x = Student("Johnny", "Shay")
x.printname()

Note

In the example above, no additional methods and properties are added to the new class (child), so the pass statement is used to allow for the creation of a seemingly empty class (it will get the parent’s methods and properties) without throwing an error.

Output:

Johnny Shay

Using the __init()__ Function

When you add the __init()__ function, the child class will no longer inherit the parent’s __init()__ function.

class Person:
    def __init__(self, fname, lname):
        self.firstname = fname
        self.lastname = lname

    def printname(self):
        print(self.firstname, self.lastname)

class Student(Person):
    def __init__(self, fname, lname):
        Person.__init__(self, fname, lname)

x = Student("Johnny", "Shay")
x.printname()

Output:

Johnny Shay

Using the super() Function

The super() function makes the child class inherit all the methods and properties even without specifying the name of the parent element.

class Person:
    def __init__(self, fname, lname):
        self.firstname = fname
        self.lastname = lname

    def printname(self):
        print(self.firstname, self.lastname)

class Student(Person):
    def __init__(self, fname, lname):
        super().__init__(fname, lname)

x = Student("Johnny", "Shay")
x.printname()

Output:

Johnny Shay

Adding Properties to the Child Class

class Person:
    def __init__(self, fname, lname):
        self.firstname = fname
        self.lastname = lname

    def printname(self):
        print(self.firstname, self.lastname)

class Student(Person):
    def __init__(self, fname, lname):
        super().__init__(fname, lname)
        self.firstyear = 2015 #property added

x = Student("Johnny", "Shay")
print(x.firstyear)

Output:

2015

Passing Properties to the Child Class

class Person:
    def __init__(self, fname, lname):
        self.firstname = fname
        self.lastname = lname

    def printname(self):
        print(self.firstname, self.lastname)

class Student(Person):
    def __init__(self, fname, lname, year):
        super().__init__(fname, lname)
        self.firstyear = year #property will be passed

x = Student("Johnny", "Shay", 2015)
print(x.firstyear)

Output:

2015

Adding Methods to the Child Class

class Person:
    def __init__(self, fname, lname):
        self.firstname = fname
        self.lastname = lname

    def printname(self):
        print(self.firstname, self.lastname)

class Student(Person):
    def __init__(self, fname, lname, year):
        super().__init__(fname, lname)
        self.graduationyear = year

    def welcome(self): #method added
        print("Welcome", self.firstname, self.lastname, "to the freshman class of", self.graduationyear)

x = Student("Johnny", "Shay", 2025)
x.welcome()

Note

If you add a method in the child class with the same name as a function in the parent class, the inheritance of the parent method will be overridden.

Output:

Welcome Johnny Shay to the freshman class of 2025

Python Notes:

  • The most recent major version of Python is Python 3; however, Python 2 is still in use and quite popular, although not being updated with anything other than security updates
  • Python uses new lines to complete a command, as opposed to other programming languages which often use semicolons or parentheses
  • Python relies on indentation, using whitespace to define scope, such as the scope of loops, functions, and classes; other programming languages often use curly-brackets for this purpose
  • Python string methods return new values, and DO NOT change the original string
  • Python tuples are unchangeable after created (their items CANNOT be changed or re-ordered at a later point)
  • Python sets are unordered (may appear in random orders when called), unchangeable (the value of individual items cannot be changed after creation), unindexed (items cannot be referred to by index or key), and duplicates are NOT ALLOWED
  • As of v3.7, Python dictionaries are ordered and duplicates ARE ALLOWED; in v3.6 and earlier, dictionaries were unordered (did not have a defined order and could not be referred to using an index)
  • Python does not have built-in support for arrays, but Python lists can be used as pseudo “arrays”; therefore, all Python list methods will work with these pseudo “arrays”
If you like our content, and find it helpful, please consider making a small donation. Thank you!

We’d like to acknowledge that we learned a great deal of our coding from W3Schools and TutorialsPoint, borrowing heavily from their teaching process and excellent code examples. We highly recommend both sites to deepen your experience, and further your coding journey. We’re just hitting the basics here at 1SMARTchicken.