Relations between python 2.7 3 3.7, scipy, pip?

[larkypython]

Basically, I don't understand is scipy, numpy an extension on all python or a particular version of python? cause I installed python 2.7, 3.6 together with my ubuntu, and I installed pip and scipy, which is version only 0.19. And then I installed python3.7 through ppa, and I need to run it with

python3.7

, and when in python3.7, run

import scipy

, errors shows, looks like scipy is not installed at all.

the same problems goes for pip too.

Do I need to install pip for each version of python?
Do I need to install scipy, numpy for each version of python?

Thanks alot!