Standard Library Tour: math, random, string

Python 3.14 · ✓ verified by execution on 2026-07-23

Standard Library Tour

The Python Standard Library is a collection of modules that come pre-installed with Python.

The Math Module

The math module gives you common mathematical functions and constants — square roots, trigonometry, logarithms, pi, and more — backed by your platform’s fast C math library.

import math
print(math.sqrt(25.0))

Output

5.0

Your output

The math functions don’t work with complex numbers. Ask for the square root of a negative number and you get a ValueError, not a complex result — for that you’d use the cmath module instead:

import math
try:
    math.sqrt(-1.0)
except ValueError as e:
    print('ValueError:', e)

Output

ValueError: expected a nonnegative input, got -1.0

Your output

The Random Module

The random module produces pseudo-random numbers — they look random but come from a deterministic algorithm. That’s why seeding it with random.seed(42) makes the sequence repeatable, which is exactly what you want when writing tests.

You can generate random integers:

import random
random.seed(42)
print(random.randint(1, 10))

Output

Your output

Or choose a random element from a list:

import random
random.seed(42)
print(random.choice(['apple', 'banana', 'cherry']))

Output

cherry

Your output

The String Module

The string module defines handy constants for common groups of characters — like every digit, or every letter:

import string
print(string.digits)

Output

0123456789

Your output

string.ascii_letters is simply the lowercase letters followed by the uppercase ones — 52 in all:

import string
print(len(string.ascii_letters))

Output

Your output

Edge Cases

Random numbers from the random module shouldn’t be used for cryptography; use the secrets module instead.
Floating point math functions in the math module can be subject to precision issues.

Check yourself

The random module generates truly unpredictable random numbers suitable for security.

Reveal answer

It generates pseudo-random numbers that are predictable. For security, the secrets module must be used. — It generates pseudo-random numbers that are predictable. For security, the secrets module must be used.

math.sqrt(-1) will return a complex number '1j'.

Reveal answer

It raises a ValueError. The cmath module is required for complex numbers. — It raises a ValueError. The cmath module is required for complex numbers.

You can use string.ascii_letters without importing the string module.

Reveal answer

They live in the string module namespace and require an explicit import. — They live in the string module namespace and require an explicit import.

Standard library modules need to be installed with pip.

Reveal answer

They are built-in and shipped with Python by default. — They are built-in and shipped with Python by default.

Challenges

Challenge 1 +25 XP

Import the math module and use `math.hypot()` to calculate the hypotenuse of a right triangle with sides 3 and 4. Print the result.

Test 1 — expects "5.0"

Need a hint? (−25% XP)

Check the math documentation for hypot.

Show solution (0 XP)

import math
print(math.hypot(3, 4))

Challenge 2 +25 XP

Import `random` and `string`. Set the random seed to 42 using `random.seed(42)`. Choose a random letter from `string.ascii_uppercase` and print it.

Test 1 — expects "U"

Need a hint? (−25% XP)

You need to import two modules.

Show solution (0 XP)

import random
import string
random.seed(42)
print(random.choice(string.ascii_uppercase))