I am dynamically installing code during the runtime of a script by directly importing the pip module and installing a requirements.txt:
import pip
import site
import sys
# since I'm installing with --user, packages should be installed here,
# so make sure it's on the path
sys.path.insert(0, site.USER_SITE)
pip.main(["install", "--user", "package1"])
import package1
The package installs without error, but import package1 fails. If I quit the script and run it again without doing the install (since it's already been installed), it works just fine.
I've also double checked that the site.USER_SITE is where package1 was installed. Everything is on sys.path, but I still can't import it.
Well, this was a fast turnaround. I've been trying to figure this one out for a few days and finally came up with my answer a few minutes after asking on here.
If a path that does not yet exist is added to sys.path, it doesn't seem like it will ever be checked again when importing modules, even if it exists at a later point (or at least in python 2.7).
In my testing, site.USER_SITE didn't exist when I added it to sys.path. If I first made sure that that directory exists, then everything works how you would think it should:
import os
import pip
import site
import sys
# this makes it work
if not os.path.exists(site.USER_SITE):
os.makedirs(site.USER_SITE)
# since I'm installing with --user, packages should be installed here,
# so make sure it's on the path
sys.path.insert(0, site.USER_SITE)
pip.main(["install", "--user", "package1"])
import package1