Python Function decorators

1. What is a Function Decorator?

A function decorator is a function that adds extra work to another function.

In simple words:
👉 A decorator wraps a function
👉 It runs before or after the function
👉 The original function code does not change

2. Real-Life Example

Think of a mobile phone cover 📱

• Phone = function

• Cover = decorator

The cover adds protection without changing the phone.

3. Why Use Function Decorators?

We use decorators to:
✔ Add logging
✔ Add security checks
✔ Measure time
✔ Reuse code again and again

4. Function Without Decorator

Example

5. Create a Simple Function Decorator

Step 1: Create Decorator Function

Step 2: Apply Decorator

Output:

6. How @decorator Works?

This:

7. Function Decorator with Arguments

Example

8. Decorator with Multiple Arguments

Example

9. Real-Life Example: Login Check

Example

10. Using functools.wraps (Good Practice)

This keeps function name and details safe.

Example

11. Common Beginner Mistakes

❌ Forgetting to Call Function

✔ Correct:

---

❌ Forgetting to Return Wrapper

❌ Wrong.

12. Simple Practice Examples

Example 1: Time Message Decorator

Example 2: Math Decorator

Example 3: Decorator Without @

13. Summary (Python Function Decorators)

✔ Decorators modify functions
✔ Use @decorator_name
✔ Wrapper function is important
✔ Supports arguments
✔ Very powerful Python feature

📘 Perfect for Beginner & Advanced eBook

This chapter is ideal for:

• Python learners

• Interview preparation

• Real-world projects

• Writing clean code

If you want next, I can write:

• Class Decorators

• Decorator Chaining

• Advanced Decorators

• Real Python Projects

Just tell me 😊