Is there a way to save networkx 'draw' result to a file or variable instead of displaying it?

Question

I would like to generate a graph's drawing but save it to file instead of displaying it to screen. Is there a way to do that?

Answer 1

Yes! networkx will draw to a matplotlib figure, and you can use all matplotlib API thereafter, including saving the file (to chosen format and dpi).

import networkx
import matplotlib
import matplotlib.pyplot

g = networkx.Graph()
g.add_edge(1,2)
fig = matplotlib.pyplot.figure()
networkx.draw(g, ax=fig.add_subplot())
if True: 
    # Save plot to file
    matplotlib.use("Agg") 
    fig.savefig("graph.png")
else:
    # Display interactive viewer
    matplotlib.pyplot.show()

Explanatory Notes:

1. matplotlib.use("Agg") is optional. It is appropriate for programs that never want to show interactively viewer.
2. f.add_subplot() all parameters are optional:
   • 'what is the fig.add_subplot(111) argument' (stackoverflow.com)
   • api documentation matplotlib.pyplot.subplot(), explains first args parameter

Answer 2

Here is the documentation you are looking for, with many solutions. I may add that if no one is supposed to read or modify the created file (it's just a storing format), you may use pickle. If you need a more generic format because the graph will be used in other tools you may prefer graphML or Json.

Example:

>>> cube = nx.hypercube_graph(2)
>>> nx.write_gpickle(cube,"cube.gpickle")
>>> readCube = nx.read_gpickle("cube.gpickle")
>>> cube.edge
{(0, 1): {(0, 0): {}, (1, 1): {}}, (1, 0): {(0, 0): {}, (1, 1): {}}, (0, 0): {(0, 1): {}, (1, 0): {}}, (1, 1): {(0, 1): {}, (1, 0): {}}}
>>> readCube.edge
{(0, 1): {(0, 0): {}, (1, 1): {}}, (1, 0): {(0, 0): {}, (1, 1): {}}, (0, 0): {(0, 1): {}, (1, 0): {}}, (1, 1): {(0, 1): {}, (1, 0): {}}}