Understanding Inheritance in Python: A Comprehensive Guide to OOP Concepts
What is Inheritance?
-
Inheritancedescribesis a kind ofrelationship between two or more classes, abstracting common details into super class and storing specific ones in the subclass. -
To create a child class, specify the parent class name inside the pair of parenthesis, followed by it's name.
Example
class Child(Parent):
pass
- Every child class inherits all the behaviours exhibited by their parent class.
Inheritance
-
In Python, every class uses inheritance and is inherited from
objectby default. -
Hence, the below two definitions of
MySubClassare same.
Definition 1
class MySubClass:
pass
Definition 2
class MySubClass(object):
pass
-
objectis known as parent or super class. -
MySubClassis known as child or subclass or derived class.
Inheritance in Action
class Person:
def __init__(self, fname, lname):
self.fname = fname
self.lname = lname
class Employee(Person):
all_employees = []
def __init__(self, fname, lname, empid):
Person.__init__(self, fname, lname)
self.empid = empid
Employee.all_employees.append(self)
Employeeclass is derived fromPerson.
Inheritance in Action
p1 = Person('George', 'smith')
print(p1.fname, '-', p1.lname)
e1 = Employee('Jack', 'simmons', 456342)
e2 = Employee('John', 'williams', 123656)
print(e1.fname, '-', e1.empid)
print(e2.fname, '-', e2.empid)
Output
George - smith
Jack - 456342
John - 123656
- In the above example,
Employeeclass utilizes__init __method of the parent classPersonto create its object.
Extending Built-in Types
-
Inheritancefeature can be also used to extend the built-in classes likelistordict. -
The following example extends
listand createsEmployeesList, which can identify employees, having a given search word in their first name.
Example 1
class EmployeesList(list):
def search(self, name):
matching_employees = []
for employee in Employee.all_employees:
if name in employee.fname:
matching_employees.append(employee.fname)
return matching_employees
Extending Built-in Types
Extending Built-in Types EmployeesList object can be used to store all employee objects, just by replacing statement all_employees = [] with all_employees = EmployeesList().
Example 2
class Employee(Person):
all_employees = EmployeesList()
def __init__(self, fname, lname, empid):
Person.__init__(self, fname, lname)
self.empid = empid
Employee.all_employees.append(self)
e1 = Employee('Jack', 'simmons', 456342)
e2 = Employee('George', 'Brown', 656721)
print(Employee.all_employees.search('or'))
Output
['George']