How to get the distance from one vertex to other vertex along the normal polygon?

I need to get a distance from the vertex to the vertex along the normal of the polygon.
Look, I’ve got a polygon that I want to move to its normal to any too. In this case, I move the polygon with index 36 to the vertex with index 31 to the normals. I just include snapping to the vertex with the closest parameter. I get the distance of 0.3568.

How can I reach the distance of 0.3568 between the 30 and 31 vertex using Python?

Good that this got solved so quickly. Darcvizer, just note that asking the same question in two forums at once is often considered rude.