Defining a decorator

Your buddy has been working on a decorator that prints a "before" message before the decorated function is called and prints an "after" message after the decorated function is called. They are having trouble remembering how wrapping the decorated function is supposed to work. Help them out by finishing their print_before_and_after() decorator.

This exercise is part of the course

Writing Functions in Python

Exercise instructions

Call the function being decorated and pass it the positional arguments *args.
Return the new decorated function.

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

def print_before_and_after(func):
  def wrapper(*args):
    print('Before {}'.format(func.__name__))
    # Call the function being decorated with *args
    ____(*args)
    print('After {}'.format(func.__name__))
  # Return the nested function
  return ____

@print_before_and_after
def multiply(a, b):
  print(a * b)

multiply(5, 10)

Edit and Run Code

This exercise is part of the course

Writing Functions in Python

IntermediateSkill Level

4.8+

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The goal of this course is to transform you into a Python expert, and so the first chapter starts off with best practices when writing functions. You'll cover docstrings and why they matter and how to know when you need to turn a chunk of code into a function. You will also learn the details of how Python passes arguments to functions, as well as some common gotchas that can cause debugging headaches when calling functions.

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Exercise 1: Using context managers Exercise 2: The number of cats Exercise 3: The speed of cats Exercise 4: Writing context managers Exercise 5: The timer() context manager Exercise 6: A read-only open() context manager Exercise 7: Advanced topics Exercise 8: Context manager use cases Exercise 9: Scraping the NASDAQ Exercise 10: Changing the working directory

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Current Exercise

Now that you understand how decorators work under the hood, this chapter gives you a bunch of real-world examples of when and how you would write decorators in your own code. You will also learn advanced decorator concepts like how to preserve the metadata of your decorated functions and how to write decorators that take arguments.

Exercise 1: Real-world examples Exercise 2: Print the return type Exercise 3: Counter Exercise 4: Decorators and metadata Exercise 5: Preserving docstrings when decorating functions Exercise 6: Measuring decorator overhead Exercise 7: Decorators that take arguments Exercise 8: Run_n_times()Exercise 9: HTML Generator Exercise 10: Timeout(): a real world example Exercise 11: Tag your functions Exercise 12: Check the return type Exercise 13: Great job!