Finding execution time

import time, random

class ExecutionTime:

  def __init__(self):

    self.start_time = time.time()

  def duration(self):

    return time.time() - self.start_time

timer = ExecutionTime()

L = [random.randint(1, 888898) for i in range(1, 10_000_000)]

print(f'Finished in {timer.duration()} seconds.')