This is close to what pipenv does. It also adds dependency management. If one subdependency is library_a > 1.0, and another is library_b < 2.0 while also e.g.

This is close to what pipenv does. It also adds dependency management. If one subdependency is library_a > 1.0, and another is library_b < 2.0 while also e.g. 2.1 exists, then it will try to find a version between 1.0 and 2.0. Pip doesn't do that. So in my mind, that's what pipenv is -- pip, virtualenv, those two files, plus dependency management.