This content originally appeared on DEV Community and was authored by Tess Mueske
Writing dry code is important. DRY is a handy acronym meaning Don't Repeat Yourself. Dry code is more legible and easily understood by others, making you a better developer! Dry code avoids boilerplate code, which is code that is written again and again without much change.
Decorators are a powerful resource for developers wanting to write dry code in Python. A decorator is a way to package code into a reusable function. They can be used before functions, classes, or methods. In this post, we'll be covering function decorators.
A decorator is a function that takes another function as an argument and returns a new function in its output.
How to make a decorator function
Decorators take in another function as an argument.
def function_1():
print("Hi")
def function_2(_f_):
#function_2 is the decorator!
another_function() #continue reading below to see what this function is....
Inside the decorator function, there's a second function called a wrapper function.
The wrapper function is a nested function, meaning it's a function inside of a function.
The wrapper function is what adds the desired behavior.
def example_decorator(function):
def wrapper_function(parameter1):
print("Start")
val = function(parameter1) # this calls the function passed to example_decorator
print("End")
return val
return wrapper_function
So, let's put it all together:
def example_decorator(function):
def wrapper_function(parameter1):
print("Start")
val = function(parameter1) # this calls the function passed to example_decorator
print("End")
return val
return wrapper_function
def print_hello(message):
print(f"{message}")
print_hello = example_decorator(print_hello)
#^^the variable name (here it's print_hello) can be anything you want. This is called function aliasing.
Then, when you call print_hello, you get....
print_hello("Hello"):
# Output:
# Start
# Hello
# End
Wooooo!
Reusability
When you want to re-use the function, you activate it at any point in your code using an 'at' symbol: @. The code beneath the @ is then run through the function we defined previously.
@example_decorator
def print_hello(message):
print(f"{message}")
# Calling the decorated function:
print_hello("Hi")
# Output:
# Start
# Hi
# End
Whew, that was a lot!
Function decorators are a challenging part of coding in Python! This stuff is hard, and you are doing great. :)
Sources:
Flatiron School material
https://www.youtube.com/watch?v=BE-L7xu8pO4
https://www.youtube.com/watch?v=WpF6azYAxYg
https://www.youtube.com/watch?v=r7Dtus7N4pI
This content originally appeared on DEV Community and was authored by Tess Mueske
Tess Mueske | Sciencx (2024-08-04T21:52:36+00:00) Function Decorators in Python. Retrieved from https://www.scien.cx/2024/08/04/function-decorators-in-python/
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