Python Decorator

DECORATOR SYNTAX

1- Define a decorator

def decorator_function(function):
    def wrapper_function():
        # Do something before the function
        function()
        # Do something after the function
    return wrapper_function

Python Decorator Function (4 lines of code)

1- Create a normal function.
2- Input is another normal function, the function in this case doesn't have parentheses ().
3- Inside the decorator_function, create a wrapper_function
The wrapper_function() will trigger the actual input "function()" that was passed into the decorator_function().
4- Return the wrapper_function without parentheses ().

Key takeaways:

  + Decorator function is just a function that wraps another function,
  + And GIVE that function some ADDITIONAL FUNCTIONALITY

2.1 - Using a decorator function by @ sign -> RECOMMENDED way.

@decorator_function #this line will trigger the decorator function for a_normal_function
def a_normal_function():
    pass

2.2 - Using a decorator function by input function -> NOT RECOMMENDED way.

decorated_func = decorator_function(a_normal_function)
decorated_func() # remember to add parentheses ()

EXAMPLES

Requirements:

• All functions should be delayed by 5 seconds.
• Avoid adding time.sleep(5) to each function.
• Add time.sleep(5) once.

Implementation:

We can modify delay_decorator to delay the execution of the wrapped function by 5 seconds.

import time

def delay_decorator(function):
    def wrapper_function():
        time.sleep(5) # wait 5 seconds before executing the next function
        function()
    return wrapper_function


@delay_decorator
def say_hello():
    print("Hello!")

@delay_decorator
def say_bye():
    print("GoodBye!")

def say_greeting():
    print("How are you?")

Now we will define a main_flow:

def main_flow():
    say_hello() # no delay because we don't add @delay_decorator to it
    say_greeting() # delay 5s before executing greeting
    say_bye() # delay 5s before executing GoodBye

main_flow()

Result:

Hello!
wait 5s
How are you?
wait 5s
GoodBye!