How to Install Python Packages using a Script

Warning:

Use of a Python script to run pip to install a package is not supported by the Python Packaging Authority (PyPA) for the following reason:

• Pip is not thread-safe, and is intended to be run as a single process. When run as a thread from within a Python script, pip may affect non-pip code with unexpected results.

However, PyPA fully supports using a Python script to run pip as a subprocess. 

Python Installation Checklist

Before packages can be installed, ensure that a Python installation containing the necessary files needed for installing  packages is in place by following the Installation Requirements.

How to Run Pip as a SubProcess

When it comes to automating the installation of Python packages, you can create a Python script that runs pip as a subprocess with just a few lines of code:

import sys
import subprocess
# implement pip as a subprocess:
subprocess.check_call([sys.executable, '-m', 'pip', 'install', '<packagename>'])

The package, as well as any requirements will be installed. 

• Note: pip installs wheels by default. Wheels include package requirements. If pip does not find a wheel to install, it will build one.

Interactive Usage

If you’re running the script interactively, it’s good practice to confirm the installation. The following script will run pip as a subprocess to install one or more packages, and then print an updated list of installed packages:

import sys
import subprocess
# implement pip as a subprocess:
subprocess.check_call([sys.executable, '-m', 'pip', 'install', '<packagename>'])
# process output with an API in the subprocess module:
reqs = subprocess.check_output([sys.executable, '-m', 'pip', 'freeze'])
installed_packages = [r.decode().split('==')[0] for r in reqs.split()]
print(installed_packages)

How to run Conda as a SubProcess

If you’re working with Anaconda’s version of Python, you can also run Anaconda’s package manager (conda) as a subprocess in order to install Python packages. The following Python script provides an example:

import sys
import subprocess
import conda.cli.python_api as Conda
# implement conda as a subprocess:
subprocess.check_call([sys.executable, '-m', 'conda', 'install', '<packagename>'])

The specified package(s), along with any requirements will be installed and displayed as output.

Next Steps

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