A decorator that prints how long a function took to run.

timer.py

import time
from functools import wraps

def timer(func):
  """A decorator that prints how long a function took to run."""
  
  @wraps(func)
  def wrapper(*args, **kwargs):
    # When wrapper() is called, get the current time.    
    t_start = time.time()
    # Call the decorated function and store the result.    
    result = func(*args, **kwargs)
    # Get the total time it took to run, and print it.    
    t_total = time.time() - t_start    
    print('{} took {}s'.format(func.__name__, t_total))
    return result
 return wrapper

@timer
def sleep_n_seconds(n):  
  time.sleep(n)
  
sleep_n_seconds(5) # sleep_n_seconds took 5.0050950050354s