planarity

library0.6pypypi✓ verified 83d ago

Planarity is a Python package for testing and manipulating the planarity of undirected graphs. It wraps the Boyer-Myrvold planarity algorithm (C library) and provides functions like is_planar, kuratowski_subgraph, and planar_embedding. The current version is 0.6, released with Cython 3 support, but the library is in maintenance mode with infrequent updates.

data

pip install planarity

github ↗package ↗

INSTALL

IMPORT

SIG · PLANARITY

planarity

datapythonv0.6

Install

—

Import

—

Disk

—

Pass rate

0/ 10

Env Coverage0 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v? · pip install

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

build_error

glibc

py 3.10–3.95 runs

build_error

Code

Verified usage

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

planarity

✓ import planarity

The top-level module is named 'planarity'. No subpackage import.

Simple test of planarity for the non-planar graph K5.

import planarity def test_planarity(): # Example: complete graph K5 is non-planar edges = [(0, 1), (0, 2), (0, 3), (0, 4), (1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)] # Check planarity result = planarity.is_planar(edges) print('Is K5 planar?', result) # False test_planarity()

Debug

Known issues

breakingIn version 0.4, inputs with parallel edges are silently dropped with a warning. This can cause incorrect results or confusion. Always deduplicate edges before calling planarity functions.

fix

Remove parallel edges using set operations: edges = list(set((min(u,v), max(u,v)) for u,v in edges))

affects: >=0.4

brokenThe library uses Cython and requires compilation. On some platforms (e.g., Windows without a C compiler), installation may fail with a 'Unable to find vcvarsall.bat' error.

fix

Install from a precompiled wheel if available, or use conda; alternatively, use the Cython source and ensure a C compiler is properly configured.

affects: all

gotchaThe function kuratowski_subgraph() may raise a KeyError if the graph is planar. It is designed to be called only for non-planar graphs, but the documentation is unclear. Always check is_planar first.

fix

if not planarity.is_planar(edges): sub = planarity.kuratowski_subgraph(edges)

affects: all

Errors

Common errors & fixes

ImportError: No module named 'planarity'

The package is not installed or the Python environment is incorrect.

fix

Run 'pip install planarity' in the correct environment.

FileNotFoundError: [Errno 2] No such file or directory: 'planarity.c'

The Cython-generated C file is missing from the source distribution (common with older pip or setuptools).

fix

Install with '--no-cache-dir' or upgrade pip: 'pip install --upgrade pip && pip install planarity'

KeyError: 0

The planarity library expects integer vertices starting from 0. Non-consecutive or non-integer vertices (like strings) may cause this error.

fix

Remap vertices to consecutive integers starting at 0 before calling planarity functions.

Upgrade

Version history

0.6latest on PyPI · released Jul 6, 2024

Audit

Dependencies

cythonrequiredRequired to compile the included Cython source (planarity.pyx). Planarity 0.4.1+ requires cython for build.

Agent activity

10 hits · last 30 days

node

Resources

githubhttps://github.com/hagberg/planarity ↗

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