How to access the road graph plugin in python?

Question

I am developing a few scripts in Python for QGIS 1.8 to automate some geo-tasks and one of them would be to calculate the shortest distance from a hospital to each building in a town.

I would like to take advantage of the already existing Qgis plugin but, as it is a C++ plugin, I am not sure whether it is possible to access it from Python? Is there a binding or a trick for that?

If not, any further advice would be appreciated! As the base data is OpenStreetMap data stored in a PostGIS DB, I may also try with pgRouting. But the QGIS plugin would be my favourite choice if possible.

PS: this question is close to this one: Is there a way to access QGIS plugins in Python? but I believe it's still different enough to be worth a new thred.

Answer 1

gis-lab.info has a tutorial on using the network analysis library in QGIS using Python. It's not in English but Google Translate should be able to make it comprehensible. Good luck!

• Stéphane Henriod: The Google translation doesn't really help, cause it's a very poor translation. But using your examples of code, I somehow manage to get it through. спасибо
• R.K.: Btw, that wasn't my blog post. I just linked it. Glad to know it helped though. Did it answer your question?
• Stéphane Henriod: I'm still working on it but I think it did solve it yes, thx

Answer 2

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There's a tutorial for the Network analysis library in the QGIS documentation that covers building a routing graph as well as shortest path and service area calculations.

Answer 3

You can find multiple versions of routing scripts which use the QGIS network analysis library in my Github repository, e.g. https://github.com/anitagraser/QGIS-Processing-tools/blob/master/2.2/scripts/point_layer_to_route.py which converts an ordered set of points into a route.