kiwisolver

library1.5.0pypypi✓ verified 25d ago

Kiwisolver is a fast implementation of the Cassowary constraint solver, designed to be lightweight and efficient. The current version is 1.5.0, released on March 9, 2026. The library is actively maintained and follows a regular release cadence, with updates approximately every few months.

data serialization

pip install kiwisolver

github ↗package ↗docs ↗changelog ↗

INSTALL

IMPORT

SIG · KIWISOLVER

kiwisolver

datapythonv1.5.0

Install

1.8s avg

Import

—

Disk

22MB

Pass rate

10/ 10

Env Coverage10 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v1.5.0 · 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 3.10–3.95 runs

installs and imports cleanly · install 0.0s · import 0.000s · 24.8MB

glibc

py 3.10–3.95 runs

installs and imports cleanly · install 1.8s · import 0.000s · 25MB

22MB installed

● package 22MB

Code

Verified usage

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

Solver

✓ from kiwisolver import Solver

Ensure correct import path to access the Solver class.

A basic example demonstrating how to set up and solve a constraint system using Kiwisolver.

import os from kiwisolver import Solver solver = Solver() # Define variables and constraints here solver.update() # Solve the system solution = solver.solve() print(solution)

Debug

Known issues

breakingKiwisolver requires Python 3.10 or higher.

fix

Upgrade your Python installation to version 3.10 or later.

affects: >=1.5.0

gotchaEnsure that the 'cppy' package is installed for Python bindings.

fix

Install the 'cppy' package using pip.

affects: >=1.5.0

breakingThe `kiwisolver.Solver` object does not have an `update` method. This often indicates an incorrect API usage or an expectation of a method that is not part of the `kiwisolver` library's standard interface.

fix

Consult the `kiwisolver` documentation for available methods and correct API usage. Common methods for solving or updating variables include `solve()` or `updateVariables()`.

affects: >=1.0.0

Errors

Common errors & fixes

error: Microsoft Visual C++ 14.0 or greater is required. Get it with "Microsoft C++ Build Tools": https://visualstudio.microsoft.com/visual-cpp-build-tools/

On Windows, kiwisolver requires the Microsoft Visual C++ Build Tools to compile its C++ extensions during installation.

fix

Download and install the "Build Tools for Visual Studio" from Microsoft's website, ensuring the "Desktop development with C++" workload is selected during installation.

fatal error: Python.h: No such file or directory

On Unix-like systems, kiwisolver requires the Python development headers to compile its C++ extension, but these headers (specifically Python.h) are missing.

fix

Install the Python development package for your specific Python version using your system's package manager (e.g., `sudo apt-get install python3-dev` on Debian/Ubuntu, or `sudo yum install python3-devel` on CentOS/Fedora).

ModuleNotFoundError: No module named 'kiwisolver'

The kiwisolver package is either not installed in the current Python environment, or the environment in which it was installed is not the one being used.

fix

Install the package using pip: `pip install kiwisolver`, and ensure you are running your script in the correct virtual environment if one was used during installation.

Upgrade

Version history

1.5.0latest on PyPI · released Mar 9, 2026

Audit

Dependencies

cppyrequiredRequired for Python bindings to the C++ codebase

Agent activity

7 hits · last 30 days

node

Resources

githubhttps://github.com/nucleic/kiwi ↗

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

docshttps://kiwisolver.readthedocs.io/en/latest/ ↗

changeloghttps://github.com/nucleic/kiwi/blob/main/releasenotes.rst ↗