Recently, I needed the capability to install a package from PyPI via the pip package manager from within a Python script and use it from within the very same script. As it was a bit trial and error and I had to go through several different sites and posts to finally find a working solution, I thought I’d share it here (aka so that I’ll be able to copy and paste this the next time I need it myself 👿):

def install_pip_package(pkg, install_name=None):
    import importlib
    import sys
    from subprocess import check_call
    import site

    try:
        importlib.import_module(pkg)
    except ImportError:
        if install_name is None:
            install_name = pkg
        check_call([
            sys.executable,
            "-m", "pip", "install", install_name
        ])
        importlib.reload(site)
    finally:
        importlib.import_module(pkg)

Okay, so that’s the whole magic. By default, you can call this function like this:

# Ensure `termcolor` is installed:
install_pip_package("termcolor")

# Now we can safely import it:
import termcolor

In case the name for importing the module and installing it via pip differ, you can call it like this:

# Ensure the `dialog` module is available, if not, install it,
# but keep in mind it is called `pythondialog` in PyPI:
install_pip_package("dialog", install_name="pythondialog")

# Now we can safely use it:
import dialog

As I like to explain things, here some words on the function itself:

• We try to import the desired module to see if it already is there.
• If this yields an ImportError, we know it is not present. In this case, we de facto use python -m pip install <install_name> to install it.
• If this succeeds, we explicitly reload the site module, which ensures that the next attempt to import the just installed module will in fact find it.

Well, that’s it. Maybe a site note that such an approach will not replace proper deployment and packaging dependencies as an app. But in environments like the one I needed this for, it is super handy 😉

Martin Hoeher

I am a software/firmware developer, working in Dresden, Germany. In my free time, I spent some time on developing apps, presenting some interesting findings here in my blog.