Enumeration of proper vertex colorings on an undirected graph. Requires Python 3.8 or later.
Usage: color.py [OPTIONS]
Check whether graph is colorable.
Options:
-f, --filename FILE The file containing the graph specification.
[required]
-c, --colors INTEGER The number of colors to use. [required]
-a, --useall Use at least one of each color. Off by default.
--help Show this message and exit.
The graph is internally represented as an edge set.
Graph file should be in DIMACS format for undirected graphs. Nodes are number from 0 up to num_vertices - 1.
c This is a comment line. They being with c.
c The next line declares 4 vertices and 3 edges.
p color 4 3
c Each line afterward should start with e to describe edges.
e 0 1
e 1 3
e 2 1
Saving this information into a file tmp.txt, we then execute the coloring program.
$ python color.py -f tmp.txt -c 5
Graph with 4 vertices, 3 edges.
{0, 1}
{1, 3}
{1, 2}
There are 320 5-colorings.
You can iterate through the colorings themselves with Graph.colorings.
Run pytest for a series of parametrized unit tests for complete, cycle, edgeless, and path graphs. Validity is checked using chromatic polynomials.