If you try to find library on Google about how python (or Django, Flask) can easily calculate latitude longitude points distance, you probably got geopy or pyproj.
Yes, previously I used pyproj , because years ago I have quite alot experience with Proj4 library . And it's quite hard to use pyproj in windows, you have to install SDK an so on.
What a great project (pyproj) because of the precision of its calculation.
don't belive me? it's ok, you can visit this geodesic calculation  to prove it. Or follow this discussion .