feat: expose voronoi to python

[BeaMarton13]

I used Cody for the functions.

• By submitting this pull request, I assign the copyright of my contribution to The igraph development team.

[ntamas]

Try to avoid re-formatting the .py files even if your IDE insists on reformatting. It makes it much harder to go through the PR and separate pure formatting-only modifications from the "real" part of the PR.

[szhorvat]

Only a few comments, not an exhaustive review.

[ntamas]

Not a full review yet, I haven't checked the unit test and the Python side in detail. From a bird's eye view the Python side looks good.

[szhorvat]

I think modularity should not be a parameter. Instead, let modularity be computed unconditionally. This takes little time compared to the rest of the algorithm.

[Copilot]

Pull Request Overview

This PR introduces the Voronoi‐based community detection algorithm to the Python igraph API, providing both C and Python bindings and adding basic tests to validate its behavior.

• Expose community_voronoi in the C library and register it in Graph
• Add a Python wrapper _community_voronoi in community.py
• Add testVoronoi unit tests for simple graph scenarios

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
tests/test_decomposition.py	New testVoronoi method with three basic cases
src/igraph/community.py	Added _community_voronoi Python wrapper
src/igraph/init.py	Registered community_voronoi in Graph
src/_igraph/graphobject.c	Implemented igraphmodule_Graph_community_voronoi

Comments suppressed due to low confidence (2)

src/igraph/community.py:372

• The docstring for mode does not mention the total alias that is supported in mode_map. Update the parameter description to include "total" as an alias for "all".

        mode_map = {"out": "out", "in": "in", "all": "all", "total": "all"}  # alias

tests/test_decomposition.py:538

• [nitpick] The tests only cover the default parameters. Consider adding cases for non‐unit lengths, non‐unit weights, non‐default mode, and a custom radius to fully exercise the new API.

    def testVoronoi(self):

[szhorvat]

Thanks for all your work on this so far @BeaMarton13 !

There are some warnings when building docs. Can you help me by investigating the cause?

WARNING: /Users/szhorvat/Repos/python-igraph/.venv/lib/python3.13/site-packages/igraph/_igraph.abi3.so:???: Cannot parse signature of igraph._igraph.GraphBase.community_voronoi
WARNING: /Users/szhorvat/Repos/python-igraph/.venv/lib/python3.13/site-packages/igraph/community.py:333: Cannot find link target for "igraph.Graph.ecc"
WARNING: /Users/szhorvat/Repos/python-igraph/.venv/lib/python3.13/site-packages/igraph/_igraph.abi3.so:???: Documented parameter "lengths" does not exist
WARNING: /Users/szhorvat/Repos/python-igraph/.venv/lib/python3.13/site-packages/igraph/_igraph.abi3.so:???: Documented parameter "weights" does not exist
WARNING: /Users/szhorvat/Repos/python-igraph/.venv/lib/python3.13/site-packages/igraph/_igraph.abi3.so:???: Documented parameter "mode" does not exist
WARNING: /Users/szhorvat/Repos/python-igraph/.venv/lib/python3.13/site-packages/igraph/_igraph.abi3.so:???: Documented parameter "radius" does not exist
WARNING: /Users/szhorvat/Repos/python-igraph/.venv/lib/python3.13/site-packages/igraph/__init__.py:3993: Cannot find link target for "igraph.Graph.ecc"

[szhorvat]

There are some warnings when building docs. Can you help me by investigating the cause?

WARNING: /Users/szhorvat/Repos/python-igraph/.venv/lib/python3.13/site-packages/igraph/_igraph.abi3.so:???: Cannot parse signature of igraph._igraph.GraphBase.community_voronoi
WARNING: /Users/szhorvat/Repos/python-igraph/.venv/lib/python3.13/site-packages/igraph/community.py:333: Cannot find link target for "igraph.Graph.ecc"
WARNING: /Users/szhorvat/Repos/python-igraph/.venv/lib/python3.13/site-packages/igraph/_igraph.abi3.so:???: Documented parameter "lengths" does not exist
WARNING: /Users/szhorvat/Repos/python-igraph/.venv/lib/python3.13/site-packages/igraph/_igraph.abi3.so:???: Documented parameter "weights" does not exist
WARNING: /Users/szhorvat/Repos/python-igraph/.venv/lib/python3.13/site-packages/igraph/_igraph.abi3.so:???: Documented parameter "mode" does not exist
WARNING: /Users/szhorvat/Repos/python-igraph/.venv/lib/python3.13/site-packages/igraph/_igraph.abi3.so:???: Documented parameter "radius" does not exist
WARNING: /Users/szhorvat/Repos/python-igraph/.venv/lib/python3.13/site-packages/igraph/__init__.py:3993: Cannot find link target for "igraph.Graph.ecc"

@BeaMarton13, I just fixed this, please see the last commit (7c30c6c). It's something very easy to miss.

[szhorvat]

@ntamas I believe this is ready. Please have a look and merge. Please use only squash-and-merge as the commit history is a mess!

[ntamas]

Thanks!