Understanding the results of Python's timeit module

Question

I'm new to using Python's timeit module to benchmark code, but the results I'm getting make me think that I'm misunderstanding how to interpret the results.

This question has two parts:

Part A. In the code below, I'm using timeit to measure the speed of Python's sort() method for lists. In the below example, I'm sorting an empty list:

import timeit

setup_code = '''
array = []
'''

test_code = ''' 
array.sort()
'''

print(timeit.timeit(stmt=test_code, setup=setup_code, number=1))

I get results like 4.437984898686409e-06 and 2.2110179997980595e-06. My understanding is that this is the number of seconds. But here's the thing: I get these results instantaneously. That is, as soon as I hit enter, that number appears on my screen. Shouldn't I, by definition, have to wait sometime between 2 and 4 seconds before I see those results?

Part B. Below, I measure the speed of sorting a list containing thousands of random integers:

import timeit

setup_code = '''
import random

array = []
for i in range(100000):
    n = random.randint(1, 100000)
    array.append(n)
'''

test_code = ''' 
array.sort()
'''

print(timeit.timeit(stmt=test_code, setup=setup_code, number=1))

Here, I get what seem to be more accurate results like 0.02303651801776141. But why is timeit telling me that sorting a large list is much faster than sorting an empty list?

Thank you in advance for your help! I'm using a Macbook Air, and getting the same results in both Python 2.7 and Python 3.11.

Answer 1

4e-06 is in scientific notation. It means 4*10**-6; timeit is telling you that sorting an empty list takes two to four microseconds.

Answer 2

My guess is that when it returns these: 4.437984898686409e-06 and 2.2110179997980595e-06. It actually returns 4.43... x 10^(-6), which would be 0.0000044379 seconds. So I'd say that's why you are getting confused.

A converter to help you understand better (copy the time you get with "e" and paste it) https://www.calculatorsoup.com/calculators/math/scientific-notation-converter.php