Interesting. I haven't used pipenv on any very large projects, but I'm surprised to hear about the slowness. With the (admittedly small) projects I've tried it, I found that it does more or less just work.
As I understand it, the problem is that Pipenv needs to resolve the dependency tree to do just about anything; however, the dependency tree is dynamic—to determine a package’s dependencies, you have to download the package and run it’s setup.py. To get the whole tree, you have to recursively download and run each package. So the cost is proportional to the size of the dependency tree, so it’s very plausible that it works fine for the smallest projects.
