Decorators in Python

What are Decorators in Python?

Decorators in Python means a decorator adds extra behavior to a function without changing the original function code.

In real programs, this topic helps in adding logging or timing. Learn the idea first, then type the program yourself and compare the output.

Why should you learn this?

• It is useful for adding logging or timing.
• It connects with checking permissions.
• It improves your ability to read, write and debug Python programs.

Important Terms

These terms are used directly in this lesson. Understand them before memorising the code.

Syntax / Basic Pattern

The simple pattern is: prepare data, apply the concept, then show the result.

def simple_logger(func):
    def wrapper():
        print("Function started")
        func()
        print("Function ended")
    return wrapper
@simple_logger
def greet():

Complete Example Program

def simple_logger(func):
    def wrapper():
        print("Function started")
        func()
        print("Function ended")
    return wrapper

@simple_logger
def greet():
    print("Hello Python")

greet()

Expected Output

Program Explanation

• def simple_logger(func): creates a reusable function.
• def wrapper(): creates a reusable function.
• print("Function started") displays information or calculated result on the screen.
• func() performs the next step of the program logic.
• print("Function ended") displays information or calculated result on the screen.
• return wrapper sends a result back from the function.
• @simple_logger performs the next step of the program logic.

Where will you use it?

• Adding logging or timing.
• Checking permissions.
• Reusing extra behaviour.

Common Mistakes

• Making code complex when a simple function or class is enough.
• Not handling possible errors or edge cases.
• Mixing project dependencies instead of using a virtual environment.

Practice Tasks

1. Type the program in decorators.py and run it.
2. Change input values or sample data and observe the new output.
3. Create one example related to adding logging or timing.
4. Write 5 lines explaining the logic in your own words.

Summary

Decorators in Python is not a theory-only topic. You should be able to explain the meaning, write the example, run it successfully, and use it in a small practical program.