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How can I make a chain of function decorators in Python?

Anonymous User 2159 11-May-2015
How can I make two decorators in Python that would do the following?
@makebold
@makeitalic
def say():
   return "Hello"
which should return
<b><i>Hello</i></b>
I'm not trying to make HTML this way in a real application, just trying to understand how decorators and decorator chaining works.
python python 
Updated on 01-May-2023
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2 Answers

Aryan Kumar

Aryan Kumar

01-May-2023

In Python, you can make a chain of function decorators by applying multiple decorators to a single function. Each decorator modifies the behavior of the function in some way.

Here's an example of how to create a chain of decorators:

def decorator1(func):
   def wrapper(*args, **kwargs):
       print("Decorator 1")
       return func(*args, **kwargs)
   return wrapper
def decorator2(func):
   def wrapper(*args, **kwargs):
       print("Decorator 2")
       return func(*args, **kwargs)
   return wrapper
@decorator1
@decorator2
def my_function():
   print("Hello, world!")
my_function()

In this example, we define two decorators, decorator1 and decorator2, each of which adds a message to the output of the function it decorates. We then apply both decorators to the my_function function using the @ syntax.

When we call my_function(), Python applies the decorators in the order they are listed, so decorator2 is applied first, followed by decorator1. Finally, the original my_function is called, and its output is modified by each decorator in turn. The output of this program is:

Decorator 1
Decorator 2
Hello, world!

You can add as many decorators to a function as you like, as long as they are listed in the order you want them to be applied. Each decorator should return a new function that wraps the original function, and the final decorator should return the modified function.

 

 


 

Anonymous User

Anonymous User

11-May-2015
Check out the documentation to see how decorators work. Here is what you asked for:
def makebold(fn):
    def wrapped():
        return "<b>" + fn() + "</b>"
    return wrapped
def makeitalic(fn):
    def wrapped():
        return "<i>" + fn() + "</i>"
    return wrapped
@makebold
@makeitalic
def hello():
    return "hello world"
print hello() ## returns <b><i>hello world</i></b>

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