best way to monitor amount of time something is on for and store it python code example

Example 1: how to time python code

from timer import Timer
t = Timer()
t.start()
# Run stuff here.
t.stop()

Example 2: python timer

import time
timer_length = float(input("How many seconds would you like you're timer to be set for? "))
time.sleep(timer_length)
print("Done!")