Decorators

In Chapter 5, Saving Time and Memory, I measured the execution time of various expressions. If you recall, I had to initialize a variable to the start time, and subtract it from the current time after execution in order to calculate the elapsed time. I also printed it on the console after each measurement. That was very tedious.

Every time you find yourself repeating things, an alarm bell should go off. Can you put that code in a function and avoid repetition? The answer most of the time is yes, so let's look at an example:

# decorators/time.measure.start.py
from time import sleep, time

def f():
    sleep(.3)

def g():
    sleep(.5)

t = time()
f()
print('f took:', time() - t)  # f took: 0.3001396656036377

t = time()
g()
print('g took:', time() - t)  # g took: 0.5039339065551758

In the preceding code, I defined two functions, f and g, which do nothing but sleep (by 0.3 and 0.5 seconds, respectively). I used the sleep function to suspend the execution for the desired amount of time...