Python Decorators

1. What is a Decorator?

A decorator is a special function that adds extra work to another function
without changing the original function code.

In simple words:
👉 A decorator wraps a function
👉 It adds something before or after the function runs

2. Why Do We Use Decorators?

Decorators help us:

• Add extra features (like logging, checking, timing)

• Keep code clean

• Avoid repeating code

3. Simple Example (Without Decorator)

Example

Now suppose we want to print something before and after this function.

4. Decorator Concept (Step by Step)

Step 1: Create a Decorator Function

Step 2: Use Decorator on a Function

Output

5. What Does @my_decorator Mean?

This line:

Means:

👉 Python automatically wraps the function.

6. Decorator with Function Arguments

Example

7. Decorator Using *args and **kwargs

This makes decorator work for any function.

Example

8. Real-Life Example: Login Check

Example

9. Decorator Without @ Syntax

You can also use decorator like this:

Example

10. Common Beginner Mistakes

❌ Forgetting Inner Function

❌ Wrong – decorator must return a function.

❌ Forgetting to Call Function

✔ Must call:

11. Simple Practice Examples

Example 1: Print Lines

Example 2: Timing Decorator (Simple)

12. Summary (Python Decorators)

✔ Decorators add extra work to functions
✔ Original function is not changed
✔ Use @decorator_name
✔ Wrapper function is required
✔ Very powerful Python feature

📘 Perfect for Beginner eBook

This chapter is ideal for:

• Python beginner books

• School & college students

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If you want next, I can write:

• Lambda Functions

• Recursion (easy)

• Modules & Packages

• Exception Handling

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