In this article, I will explain the usage of the random module in Python. As the name implies it allows you to generate random numbers.

This random module contains pseudo-random number generators for various distributions.

The function random() is one of them, it generates a number between 0 and 1.
But there are other like the functions randint(min,max) and randrange(max).

Introduction

Lets start with the absolute basic random number generation. The function random.random().
The function random() returns the next random float in the range [0.0, 1.0].

To use the random() function, call the random() method to generate a real (float) number between 0 and 1.

import random
x = random.random()
print(x)

This outputs any number between 0 and 1. For most apps, you will need random integers instead of numbers between 0 and 1.

Generate random numbers

The function randint() generates random integers for you. If you call the function, it returns a random integer N such that a <= N <= b.

The randint() method to generates a whole number (integer). You can use randint(0,50) to generate a random number between 0 and 50.

import random
x = random.randint(0,50)
print(x)

To generate random integers between 0 and 9, you can use the function randrange(min,max).

from random import randrange
print(randrange(10))

You can use randint(min,max) instead:

import random
print(random.randint(0,9))

Change the parameters of randint() to generate a number between 1 and 10.

import random
x = random.randint(1,10)
print(x)

List of random numbers

If you want to generate a list of random number, you can do so by using a for loop.
To generate a list of 100 random numbers:

import random

mylist = []

for i in range(0,100):
    x = random.randint(1,10)
    mylist.append(x)

print(mylist)

But this can be done in a much more compact way in Python, with a one liner.
The function to use is sample() which shuffles the input list, in the example below it shuffles the created list range(1,101).

That is to say, range(1,101) creates a list of numbers 1 to 100.

>>> list(range(1,101))
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100]

Then the function sample() shuffles that list in random order.

>>> import random
>>> x = random.sample(range(1,101), 100)

Choosing random items from a list

You can use the sample() method to put the list in a random order. But you can also use it get random items from a list.

If you want 3 random items from the list, you add 3 as second parameter of the sample(list) method.

import random

mylist = [1,2,3,4,5,6,7,8,9,10]
x = random.sample(mylist,3)
print(x)

If you want to pick a random item, you can use the choice(list) method. But this returns only one element.

>>> import random
>>> x = list(range(1,101))
>>> random.choice(x)
8
>>> random.choice(x)
11
>>>

You can use the method shuffle(list) to shuffle the list order and then use the first index as random number.

>>> import random
>>> x = list(range(1,101))
>>> random.shuffle(x)

The recommended way to do this is using the choice() method, but all of these work.

Reading helps, writing fixes it. PyChallenge has exercises on this and you can try them right now.