Python Constructor (init)

1. What is a Constructor?

A constructor is a special function in a class.

In Python, the constructor is called __init__().

In simple words:
👉 __init__() runs automatically
👉 It runs when an object is created
👉 It is used to set values for the object

2. Why Do We Use __init__()?

We use __init__() to:

• Give initial values to object

• Avoid writing extra code

• Make class easy to use

3. Simple Constructor Example

Example

Output:

4. Constructor with Parameters

Example

5. What is self in Constructor?

self refers to the current object.

In simple words:

 

6. Multiple Objects with Constructor

Example

7. Default Values in Constructor

Example

8. Constructor in Real Example (Bank)

Example

9. Constructor vs Normal Function

10. Common Beginner Mistakes

❌ Forgetting self

❌ Wrong.

❌ Calling Constructor Manually

❌ Not recommended.

11. Simple Practice Examples

Example 1: Book Class

Example 2: Rectangle Area

Example 3: User Profile

12. Summary (Python Constructor)

✔ __init__() is a constructor
✔ Runs automatically
✔ Sets initial values
✔ Uses self
✔ Very important in OOP

📘 Perfect for Beginner eBook

This chapter is ideal for:

• Python beginner books

• School & college students

• Self-learners

If you want next, I can write:

• Destructor (__del__)

• Inheritance

• Encapsulation

• Polymorphism

Just tell me 😊