random-numbers.md

Python by Example: Random Numbers

The random module generates pseudo-random numbers. Use it for games, simulations, sampling, and shuffling. random.random() gives a float in [0, 1). random.randint(a, b) gives an integer from a to b inclusive. Use random.seed() for reproducible results (e.g., in tests).

What you'll learn:

• random(), randint(), choice()
• shuffle() for in-place shuffling
• seed() for reproducibility

import random

# Float in [0, 1)
print(random.random())

# Integer in range (inclusive)
print(random.randint(1, 6))

# Choice from sequence
print(random.choice(["heads", "tails"]))

# Shuffle in place
items = [1, 2, 3, 4, 5]
random.shuffle(items)
print(items)

# Reproducible with seed
random.seed(42)
print(random.randint(1, 100))
random.seed(42)
print(random.randint(1, 100))

With the same seed, you get the same sequence. Useful for debugging and tests. For cryptography, use secrets instead.

To run this program:

$ python source/random-numbers.py
0.6394267984578837
4
tails
[3, 1, 4, 2, 5]
81
81

Tip: For cryptography or security-sensitive randomness, use the secrets module.

Try it: Use random.sample(items, 3) to pick 3 unique items from a list.

Source: random-numbers.py

Next: Exit