4.6. Time

The time module is another useful module. It can be used to add pauses in a program, or it can be used to time how long it takes for a program to run.

To use the time library, we import it with:

import time

4.6.1. Adding Pauses to a Program

You can add a pause to a program using time.sleep()

time.sleep(seconds)

Where seconds specifies how long the program will pause for. Here is an example.

import time

for i in range(3):
    print("tick")
    time.sleep(1)
print("BOOM!")

4.6.2. Timing a Program

The function time.time() tells us the current Unix time (time since 00:00:00 UTC on 1 January 1970) in seconds.

import time

print(time.time())

To measure the time it takes for our code to run, we check the time at the start of our code and then check the time at the end of our code. The difference in these times tells us how much time has elapsed in seconds.

import time

start = time.time()
1 + 1
end = time.time()

print(end - start)

Here it takes approximately 5e-07 seconds for the program to run. The e-07 is scientific notation for \(\times10^{-7}\), which means it takes about half a microsecond for this program to run.

Question 1

Write a program that waits a random number of seconds (up to 10) before it says Surprise!.

Solution

import random
import time

wait = random.randrange(11)
time.sleep(wait)
print('Surprise!')

random.randrange(11) will randomly select an integer from 0 (included) to 11 (not included) and store this integer in the variable wait. The program will then wait that many seconds before printing Surprise!

Question 2

Which of the following best describes the code shown below.

import random
import time

r = random.random()
while r > 0.1:
    print('Keep digging...')
    time.sleep(1)
    r = random.random()
print('Gold!')

1. It simulates digging for gold. The user has a 10% chance of finding gold each second. The program will stop once the user finds gold.

2. It simulates digging for gold. Every 0.1 seconds it will attempt to dig for gold. The program will stop once the user finds gold.

3. It simulates digging for gold. Every 1 second the program will find gold. It will continue digging indefinitely.

Solution

Solution is locked

Question 3

Which of the following programs do you think will take longer?

Program 1

for i in range(-10000, 10000, 2000):
    print(i)

-10000
-8000
-6000
-4000
-2000
0
2000
4000
6000
8000

Program 2

for i in range(-10000, 10000):
    if i % 2000 == 0:
        print(i)

-10000
-8000
-6000
-4000
-2000
0
2000
4000
6000
8000

You’ll notice that both programs give the same output.

1. Program 1 takes longer to execute than program 2.

2. Program 2 take longer to execute than program 1.

Solution

Solution is locked

Question 4

Write a program that will tell you how long it takes in seconds to perform the following calculation.

total = 1
for i in range(1, 100):
    total = total * i

Solution

Solution is locked

Code challenge: Factorial Time!

Write a program to see how long it takes for Python to calculate $5000!$. Print your answer in seconds to 6 decimal places.

Your output should look like this (with the X’s replaced by numbers):

Time: X.XXXXXX (s)

Solution

Solution is locked

Code challenge: Quick Maths

Write a program that will give the user 10 random multiplication questions from the standard multiplication tables (up to 12 x …). The program won’t move onto the next question until the user gets the first question right. The program will then print out the time (in seconds to 1 decimal place) it took the user to complete the test.

For this exercise you must:

• generate the random numbers using random.randrange(1, 13)

• get the start and end time using time.time()

Example 1: The user gets all of the questions correct.

What is 1 x 5? 5
What is 4 x 4? 16
What is 12 x 5? 60
What is 1 x 5? 5
What is 8 x 10? 80
What is 10 x 9? 90
What is 4 x 2? 8
What is 5 x 5? 25
What is 7 x 1? 7
What is 10 x 7? 70
Your time was: 11.4 seconds

Example 2: The user makes an incorrect guess on the third question and two incorrect guesses on the second last question.

What is 11 x 1? 11
What is 5 x 11? 55
What is 8 x 2? 15
16
What is 10 x 5? 50
What is 10 x 9? 90
What is 6 x 11? 66
What is 10 x 3? 30
What is 9 x 8? 72
What is 8 x 5? 32
45
40
What is 9 x 1? 9
Your time was: 17.6 seconds

Solution

Solution is locked

Code challenge: 5 Seconds

How good are you at estimating 5 seconds?

Your program should ask the user How good are you at estimating 5 seconds?. It should then tell the user to Press enter to start and then Press enter to end. The program should time how long it takes between the user pressing the enter key and tell the user the amount of time that has elapsed in seconds to 4 decimal places.

For this exercise you must:

• get the start and end time using time.time()

Example: The user presses the enter key after the Press enter to start and Press enter to end messages.

How good are you at estimating 5 seconds?
Press enter to start
Press enter to end
Time elapsed: 4.6148 seconds