4.4. Random Floats and Using Probabilities

Sometimes we want an event to occur with a specific probability. This can be achieved using random.random(). This function produces a random float between 0 (inclusive) and 1 (not inclusive), i.e. we will get a value \(r\) where \(0 \leq r < 1\).

import random

print(random.random())

We can then check whether the random value is less than or equal to \(p\), the probability with which we want the event to occur.

For example, we can write a program to generate weather conditions, which is common in a lot of games. Our simple program will say that it’s sunny 80% of the time and say that it’s rainy 20% of the time.

import random

r = random.random()
if r < 0.8:
    print("sunny")
else:
    print("rainy")

Question 1

Which of the following values could you obtain after running the following program? Select all that apply.

import random

r = random.random()
print(r*10)

1. 0
   

2. 1
   

3. 10
   

4. 0.5
   

5. 0.368479
   

6. 7.8
   

Solution

r = random.random() will produce a random float between 0 (included) and 1 (not included). Since these values get multiplied by 10, we end up with values between 0 (included) and 10 (not included).

Question 2

Write a program that will generate floats between -1 (included) and 1 (not included), i.e. will print \(r\) where \(-1 \leq r < 1\).

Solution

Solution is locked

Question 3

Which of the following best describes the purpose of the code shown below.

import random

r = random.random()
if r < 0.6:
    print('Heads')
else:
    print('Tails')

1. The program simulates a fair coin which will present Heads 50% of the time and Tails 50% of the time.

2. The program simulates an unfair coin which will present Heads 60% of the time and Tails 40% of the time.

3. The program simulates an unfair coin which will present Heads 40% of the time and Tails 60% of the time.

Question 4

Write a program that simulates a loaded dice with the following probabilities.

• 1, 2, 3, 4, 5 each appear 15% of the time

• 6 appears 25% of the time

Solution

Solution is locked

Code challenge: Fitness Wheel

Write a program that allows the user to spin the fitness wheel!

The program should display

• 10 sit ups 12.5% of the time

• 5 star jumps 12.5% of the time

• 10 squats 12.5% of the time

• 20 second plank 12.5% of the time

• 3 push ups 12.5% of the time

• 2 lunges per leg 12.5% of the time

• 30 second rest! 25% of the time

Solution

Solution is locked