Install.py for pip requirements?

I need to use one instead of a requirements.txt as I have platform specific modules.

import pip

_all_ = [
	"pick == 0.6.4",
	"requests == 2.21.0",
	"riotwatcher == 2.5.0",
]

windows = ["windows-curses", ]


def install(packages):
	for package in packages:
		pip.main(['install', package])


if __name__ == '__main__':
	from sys import platform
	install(_all_)
	if platform == 'windows':
		install(windows)

However, pip no longer can call the module main. How can I fix this without having to use pip < v9?

Thanks

Found a way:

from pip._internal import main
[...]
main(["install", PackageToInstall])