The top answers as of 2/1/2019 are outdated and no longer work with newer versions of pip.
But no worries – it’s still possible to get a list of packages programmatically:
Options:
A. _internal.main
from pip import _internal
_internal.main(['list'])
This will print out three columns with Package. Version, and Location
Note that usage of pip’s internal api is not recommended.
B. pkg_resources
import pkg_resources
print([p.project_name for p in pkg_resources.working_set])
# note that this is same as calling pip._vendor.pkg_resources.working_set
C. iter_modules
Takes a long time to execute (~300ms on computer w/ I5 CPU, SSD, & 8 gigs ram).
The benefit is that it will have a far more extensive list of modules and it will output importable names.
Ex: python-dateutil is imported as dateutil, but iter_modules will give you the importable name: dateutil
from pkgutil import iter_modules
print([p.name for p in iter_modules()])
D. Call pip in command line via subprocess
The solution to this is trivial and I’ll leave this as an exercise to the reader
aka I’m too lazy to do this, good luck! 😀