In a predict and run task you do not write code from scratch. You start from a small piece of working code, work out what you think it will do before you run it, and then run it to check whether you were right.

Random numbers change what “right” means. You cannot predict the exact number a random program will print, because nobody can. What you can predict is every number it might print, and every number it never will. That is what the prompts below ask for.

Predict

For every example, study the code carefully and write down a prediction before you touch the Run button. Your prediction should use the key terms random, import and argument, and it should list the possible outputs: the lowest, the highest, and anything in between that can never come up. You can type your prediction straight into the code as a comment, on a line starting with #.

Only once you have written your prediction should you run the code, several times, and compare the results with what you expected.

Example 1

import random

print(random.randint(1, 5))

num1 = random.randint(1, 10)
print("Your number was " + str(num1))

This prints two lines. Predict the smallest and the largest number each line can show, and whether the two numbers have to be different from each other.

Example 2

import random

print("Welcome to the dice simulator!")
num1 = random.randint(1, 6)
print("You rolled a " + str(num1))

Predict which of the three lines is the same on every run and which one changes. Then run it until you have seen both a 1 and a 6.

Example 3

import random

die = [1, 2, 3, 4, 5, 6]
num = random.choice(die)
print(num)

This is a dice roll too, written with choice instead of randint. Predict whether it can print anything Example 2 could not, and what would change if the 6 in the list were replaced with a 7.

Example 4

from random import randrange

my_number = randrange(0, 10, 2)
print(my_number)

Predict every number this can print. Then run it five times and write down the output each time. What do you notice about the five outputs? Do they have anything in common?

Example 5

Now change line 3 of the code in Example 4 so that it reads:

my_number = randrange(1, 10, 2)

Before you run the code again, write down every output you think is possible now. Then run it several times and check each result against your list.