passagemath-planarity

10.8.4 verified Fri May 01 auth: no python

Wraps the edge addition planarity suite for graph planarity testing and embedding in passagemath. Version 10.8.4, requires Python >=3.11, <3.15. Part of the passagemath ecosystem. Release cadence follows passagemath.

pip install passagemath-planarity

Common errors

error ModuleNotFoundError: No module named 'planarity' ↓

cause Importing the module directly without the passagemath namespace.

fix

Use 'from passagemath.planarity import planarity' instead of 'import planarity'.

error ModuleNotFoundError: No module named 'passagemath' ↓

cause The passagemath package is not installed.

fix

Run 'pip install passagemath-planarity' which pulls in the passagemath base package.

error UserWarning: The planarity module is experimental. API may change. ↓

cause The library might emit a warning on import; it is still usable.

fix

Suppress warnings if needed with 'import warnings; warnings.filterwarnings("ignore", message=".*experimental.*")'.

Warnings

gotcha The library is part of the passagemath ecosystem. Do not import 'planarity' directly; always use 'from passagemath.planarity import planarity'. ↓

fix Use the correct import path: from passagemath.planarity import planarity

deprecated Some older examples use 'passagemath.planarity.planarity' (duplicated module name). This still works but is redundant; the canonical import is 'from passagemath.planarity import planarity'. ↓

fix Use the recommended import: from passagemath.planarity import planarity

gotcha Requires Python >=3.11, <3.15. Installing on Python 3.15+ will fail. ↓

fix Use a Python version from 3.11 to 3.14.

Imports

planarity
wrong
```
import planarity
```
correct
```
from passagemath.planarity import planarity
```
The module is inside the passagemath namespace.

Quickstart

Quick example showing planarity test and planar embedding extraction.

from passagemath.planarity import planarity
# Test planarity of a graph given as adjacency list
# Graph: triangle with an extra isolated vertex
adj = {0: [1,2], 1: [0,2], 2: [0,1], 3: []}
result = planarity.is_planar(adj)
print(result)  # True
# Get a planar embedding
try:
    embedding = planarity.planar_embedding(adj)
    print(embedding)
except Exception as e:
    print(e)