Generate Random Numbers using Python

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).

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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)

Related Course: Complete Python Programming Course & Exercises

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.

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