fastrand

library3.1.0pypypi✓ verified 86d ago

fastrand provides significantly faster random number generation in Python compared to the standard `random` module, implemented as a C extension. It is suitable for applications where speed is critical and cryptographic security is not required. The current version is 3.0.8, with a maintenance cadence of small patches and occasional feature additions.

data

pip install fastrand

github ↗package ↗

INSTALL

IMPORT

SIG · FASTRAND

fastrand

datapythonv3.1.0

Install

1.7s avg

Import

—

Disk

16MB

Pass rate

10/ 10

Env Coverage10 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v3.1.0 · pip install

no network on importno background threads

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

py 3.10–3.910 runs

installs and imports cleanly · install 0.0s · import 0.000s · 17.8MB

glibc

py 3.10–3.910 runs

installs and imports cleanly · install 1.7s · import 0.000s · 18MB

16MB installed

● package 16MB

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

fastrand

✓ import fastrand

✗ from fastrand import random

The fastrand module is typically imported directly; its functions are accessed via 'fastrand.function_name'.

This example demonstrates how to import the fastrand module and use its primary functions: `pcg32bounded` for bounded integers, `pcg32` for unbounded 32-bit unsigned integers, and `randdouble` for floating-point numbers between 0 (inclusive) and 1 (exclusive).

import fastrand print("Random integer [0, 99]:", fastrand.pcg32bounded(100)) print("Random 32-bit unsigned int:", fastrand.pcg32()) print("Random double [0, 1):") for _ in range(3): print(f" {fastrand.randdouble():.6f}")

Debug

Known issues

gotchafastrand is NOT cryptographically secure. Do not use it for security-sensitive applications, such as generating passwords, cryptographic keys, or tokens. It uses the PCG (Permuted Congruential Generator) algorithm, which is fast but not designed for cryptographic strength.

fix

For cryptographically secure random numbers, use Python's `secrets` module (e.g., `secrets.randbelow`, `secrets.token_hex`) or `os.urandom()`.

affects: All versions

gotchafastrand is not a drop-in replacement for Python's built-in `random` module. Its API uses different function names (e.g., `pcg32bounded` instead of `randint`, `randdouble` instead of `random()`) and does not support seeding or state management in the same way.

fix

Carefully review the `fastrand` documentation for the correct function names and signatures. Do not assume `fastrand.randint()` or `fastrand.seed()` will work as they do in the `random` module.

affects: All versions

deprecatedThe `fastrand.seed()` function was present in very early versions (e.g., v0.x) but is not part of the current public API. The PCG generator in fastrand is designed to be automatically seeded, typically from system entropy upon initialization. Attempting to seed it directly via a `seed()` function will fail.

fix

Rely on fastrand's internal seeding mechanism. If explicit, repeatable seeding is required, consider using Python's standard `random` module or a different library that exposes such an API.

affects: <1.0.0 (removed). All current versions do not expose `seed()`.

Errors

Common errors & fixes

ModuleNotFoundError: No module named 'fastrand'

The fastrand library has not been installed in the current Python environment.

fix

Run `pip install fastrand` in your terminal to install the library.

AttributeError: module 'fastrand' has no attribute 'randint'

Attempting to use a function name from Python's standard `random` module (`randint`) which does not exist in the `fastrand` API.

fix

Use `fastrand.pcg32bounded(N)` to get a random integer in the range [0, N-1].

TypeError: pcg32bounded() takes exactly one argument (0 given)

The `fastrand.pcg32bounded()` function requires a single argument, which is the upper bound (exclusive) for the random integer generation.

fix

Provide a positive integer argument to `pcg32bounded()`, e.g., `fastrand.pcg32bounded(100)` for numbers 0-99.

Upgrade

Version history

3.1.0latest on PyPI · released May 15, 2026

Audit

Dependencies

No dependency data recorded yet.

Agent activity

4 hits · last 30 days

node

Resources

githubhttps://github.com/lemire/fastrand ↗

packagehttps://pypi.org/project/fastrand/ ↗