Python Library for Boyer-Myrvold planarity test or Kuratowski subgraph identification

Question

I am working with NetworkX Graphs in Python and I would like to find the Kuratowski subgraphs of any given graph which I have.

The Boyer-Myrvold planar graph testing algorithm can return an existing Kuratowski subgraph if the graph is not planar (O(n) in the number of vertices n), so I was hoping that there might already be an implementation of that algorithm or of a similar algorithm in Python. I have been so far unable to find one and I am slightly reluctant at having to re-implement it from the original research paper.

It is even better if it can easily interface with NetworkX library for graphs.

Aric · Accepted Answer · 2016-06-03T13:45:48.880

3

There is a Python wrapper for part of of John Boyer's planarity code (https://code.google.com/p/planarity/) that might be what you are looking for. It is at https://github.com/hagberg/planarity.

It has a NetworkX interface that allows you to test for planarity and find the Kurotowski subgraphs if not. e.g.

https://github.com/hagberg/planarity/blob/master/examples/networkx_interface.py

import planarity
import networkx as nx
# Example of the complete graph of 5 nodes, K5
G=nx.complete_graph(5)
# K5 is not planar
print(planarity.is_planar(G)) # False
# find forbidden Kuratowski subgraph
K=planarity.kuratowski_subgraph(G)
print(K.edges()) # K5 edges

edited Jun 03 '16 at 13:45

answered Jun 06 '15 at 03:28

Aric

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Thanks! It looks really promissing, but I can't seem to get it to work. I get the following error while trying to import it: import planarity Traceback (most recent call last): File "", line 1, in File "./planarity/planarity/__init__.py", line 2, in from .planarity import PGraph ImportError: No module named planarity – patapouf_ai Jun 09 '15 at 10:26
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I'm guessing that the problem might stem from the fact that planarity is a .pyx file and not a .py file?? – patapouf_ai Jun 09 '15 at 10:29
Ok. I solved the problem with the following steps: – patapouf_ai Jun 09 '15 at 10:38
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sudo apt-get install cython – patapouf_ai Jun 09 '15 at 10:38
and before importing planarity – patapouf_ai Jun 09 '15 at 10:38
import pyximport pyximport.install() – patapouf_ai Jun 09 '15 at 10:38
but now I get the following error while trying to import: – patapouf_ai Jun 09 '15 at 10:40
ImportError: Building module planarity.planarity failed: ["CompileError: command 'x86_64-linux-gnu-gcc' failed with exit status 1\n"] – patapouf_ai Jun 09 '15 at 10:41
actually the error is /.pyxbld/temp.linux-x86_64-2.7/pyrex/planarity/planarity.c:349:33: fatal error: src/graphStructures.h: No such file or directory #include "src/graphStructures.h" – patapouf_ai Jun 09 '15 at 11:40
it is strange, because the ./planarity/src/graphStructures.h file is there. – patapouf_ai Jun 09 '15 at 12:03
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apparently I've been complicating my life uselessly by cloning the git and importing from there. sudo pip install planarity workes and allows import. – patapouf_ai Jun 09 '15 at 12:24

Python Library for Boyer-Myrvold planarity test or Kuratowski subgraph identification

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