eWizardII eWizardII - 5 months ago 44
Python Question

graph rendering in python (flowchart visualization)

to visualize a sequence of nodes connected by edges encoded in python.

looking for a python library to visualize such graph data.

either a library written in python or python bindings, is ok

(i am aware of Visustin, but looking for alternatives)

Answer

Graphviz is the best option in my opinion.

Graphviz is the premiere graph rendering/layout library; it's mature, stable, open-source, and free of charge. It is not a dedicated flowchart or diagramming package, but it's core use case--i.e., efficient and aesthetic rendering of objects comprised of nodes and edges, obviously subsumes flowchart drawing--particularly because its api allows the user to set various constraints on the layout to encourage rendering in the various formats--eg, you can require all nodes of the same level (same number of parents from the root) to be rendered in a single center-aligned row.

Graphviz is not a python library (it's written in C); however there are high quality python bindings available.

The python-Graphviz library i am most familar with is pygraphviz, which is excellent.

The other two are pydot and yapgvb. I have used both of these at least a few times. Each is smaller than pygraphviz (which might be an advantage depending on your use case); in addition neither is documented as well as pygraphviz.

Fortunately, all three of these python libraries are thin wrappers over Graphviz, so none conceal the lightweight, elegant Graphviz syntax (the dot language).

alt text

Here's the code (in graphviz' dot langauge) i used to create the small "flowchart" below:

digraph {

  node [    fill=cornflowerblue,
            fontcolor=white,
            shape=diamond,
            style=filled];

  Step1 [   color=darkgoldenrod2,
            fontcolor=navy,
            label=start,
            shape=box];

  Step2;

  Step3a [  style=filled,
            fillcolor=grey80,
            color=grey80,
            shape=circle,
            fontcolor=navy];

  Step1  -> Step2;
  Step1  -> Step2a;
  Step2a -> Step3a;
  Step3;
  Step3a -> Step3;
  Step3a -> Step2b;
  Step2  -> Step2b;
  Step2b -> Step3;
  End [ shape=rectangle,
        color=darkgoldenrod2,
        fontcolor=navy];
  Step3  -> End [label=193];
}