Managing Application Dependencies

The package installation tutorial covered the basics of getting set up to install and update Python packages.

However, running these commands interactively can get tedious even for your own personal projects, and things get even more difficult when trying to set up development environments automatically for projects with multiple contributors.

This tutorial walks you through the use of Pipenv to manage dependencies for an application. It will show you how to install and use the necessary tools and make strong recommendations on best practices.

Keep in mind that Python is used for a great many different purposes, and precisely how you want to manage your dependencies may change based on how you decide to publish your software. The guidance presented here is most directly applicable to the development and deployment of network services (including web applications), but is also very well suited to managing development and testing environments for any kind of project.

Note

This guide is written for Python 3, however, these instructions should also work on Python 2.7.

Installing Pipenv

Pipenv is a dependency manager for Python projects. If you’re familiar with Node.js’ npm or Ruby’s bundler, it is similar in spirit to those tools. While pip alone is often sufficient for personal use, Pipenv is recommended for collaborative projects as it’s a higher-level tool that simplifies dependency management for common use cases.

Use pip to install Pipenv:

pip install --user pipenv

Note

This does a user installation to prevent breaking any system-wide packages. If pipenv isn’t available in your shell after installation, you’ll need to add the user base’s binary directory to your PATH.

On Linux and macOS you can find the user base binary directory by running python -m site --user-base and adding bin to the end. For example, this will typically print ~/.local (with ~ expanded to the absolute path to your home directory) so you’ll need to add ~/.local/bin to your PATH. You can set your PATH permanently by modifying ~/.profile.

On Windows you can find the user base binary directory by running py -m site --user-site and replacing site-packages with Scripts. For example, this could return C:\Users\Username\AppData\Roaming\Python36\site-packages so you would need to set your PATH to include C:\Users\Username\AppData\Roaming\Python36\Scripts. You can set your user PATH permanently in the Control Panel. You may need to log out for the PATH changes to take effect.

Installing packages for your project

Pipenv manages dependencies on a per-project basis. To install packages, change into your project’s directory (or just an empty directory for this tutorial) and run:

cd myproject
pipenv install requests

Pipenv will install the excellent Requests library and create a Pipfile for you in your project’s directory. The Pipfile is used to track which dependencies your project needs in case you need to re-install them, such as when you share your project with others. You should get output similar to this (although the exact paths shown will vary):

Creating a Pipfile for this project...
Creating a virtualenv for this project...
Using base prefix '/usr/local/Cellar/python3/3.6.2/Frameworks/Python.framework/Versions/3.6'
New python executable in ~/.local/share/virtualenvs/tmp-agwWamBd/bin/python3.6
Also creating executable in ~/.local/share/virtualenvs/tmp-agwWamBd/bin/python
Installing setuptools, pip, wheel...done.

Virtualenv location: ~/.local/share/virtualenvs/tmp-agwWamBd
Installing requests...
Collecting requests
  Using cached requests-2.18.4-py2.py3-none-any.whl
Collecting idna<2.7,>=2.5 (from requests)
  Using cached idna-2.6-py2.py3-none-any.whl
Collecting urllib3<1.23,>=1.21.1 (from requests)
  Using cached urllib3-1.22-py2.py3-none-any.whl
Collecting chardet<3.1.0,>=3.0.2 (from requests)
  Using cached chardet-3.0.4-py2.py3-none-any.whl
Collecting certifi>=2017.4.17 (from requests)
  Using cached certifi-2017.7.27.1-py2.py3-none-any.whl
Installing collected packages: idna, urllib3, chardet, certifi, requests
Successfully installed certifi-2017.7.27.1 chardet-3.0.4 idna-2.6 requests-2.18.4 urllib3-1.22

Adding requests to Pipfile's [packages]...
P.S. You have excellent taste! ✨ 🍰 ✨

Using installed packages

Now that Requests is installed you can create a simple main.py file to use it:

import requests

response = requests.get('https://httpbin.org/ip')

print('Your IP is {0}'.format(response.json()['origin']))

Then you can run this script using pipenv run:

pipenv run python main.py

You should get output similar to this:

Your IP is 8.8.8.8

Using pipenv run ensures that your installed packages are available to your script. It’s also possible to spawn a new shell that ensures all commands have access to your installed packages with pipenv shell.

Next steps

Congratulations, you now know how to effectively manage dependencies and development environments on a collaborative Python project! ✨ 🍰 ✨

If you find this particular approach isn’t working well for you or your use case, you may want to explore these other approaches:

If you’re interesting in creating and distributing your own Python packages, see the tutorial on packaging and distributing packages.