6.1 random Module

A module is a reusable collection of Python code. Python's built-in collection of modules is called the standard library. The random module provides tools for random numbers, random choices, and shuffling.

Importing a Module

Import a module before using it.

import random

print(random.random())
print(random.randint(1, 6))

random.random() returns a random floating-point number in [0, 1). random.randint(1, 6) returns an integer from 1 through 6, including both endpoints.

Common random Methods

Common random methods:

• random(): generate a floating-point number in [0, 1).
• randint(a, b): generate an integer in [a, b].
• choice(sequence): choose one element from a sequence.
• shuffle(list): shuffle a list in place.
• sample(sequence, k): choose k unique elements and return a new list.

Note that shuffle() mutates the original list, while sample() returns a new list.

Random Password Generator

A password generator prepares a character pool, chooses a length, repeatedly chooses random characters, and joins them into a string.

import random
import string

def password_generator(length):
    characters = string.ascii_letters + string.digits
    return "".join(random.choice(characters) for _ in range(length))

def main():
    length = int(input("Enter password length: "))
    print("Random password: %s" % password_generator(length))

if __name__ == "__main__":
    main()

One possible run:

Enter password length: 8
Random password: K2bm9Qa1