Python class constructor is used to initialize the instance of the class. Python has __init__() constructor function for the Python classes.
The method __init__( ) executes every object creation of that class. It’s a special method or member function of a class that automatically gets executes on every object creation. It is always called when an object is created.
Syntax of constructor declaration :
def __init__(self): # body of the constructor
The def keyword is used to define function.
Types of constructors
- Default Constructor – is a constructor without any parameters, however, it has a default parameter self.
- Parameterized Constructor – is a constructor with one or more parameters.
Examples Class Constructor in Python
Simple example code. Constructors also verify that there are enough resources for the object to perform any start-up task.
Creating Default Constructor Python class
This constructor has the same name as the class name.
class Test: num = 0 def __init__(self): self.num = 100 print(f'Object has created!') print(self.num) # creating object obj = Test()
Creating Parameterized Constructor
The constructor may have any number of parameters. Let’s see an example with single parameters.
class Test: i = 10 def __init__(self, value): self.i += value print(self.i) # creating object obj = Test(10)
Counting the number of objects of a class
Let’s count how many times objects are created for any class.
class Students: count = 0 def __init__(self): Students.count += 1 s1 = Students() s2 = Students() s3 = Students() print("The number of students:", Students.count)
Output: The number of students: 3
Do comment if you have any doubts and suggestions on this Python class tutorial.
Note: IDE: PyCharm 2021.3 (Community Edition)
All Python Examples are in Python 3, so Maybe its different from python 2 or upgraded versions.