Continuous Integration and Continuous Deployment

Tox can automate many testing steps for your project: running tests on various different Python versions; verifying coverage and code styles; building documentation, and so on. This is still something you would need to run by hand, and would also need to be maintained across several different versions of Python—a task made easier with tools such as pyenv (https://github.com/pyenv/pyenv), although still involving some work to keep organized.

A Continuous Integration (CI) system solves this issue by listening for changes in your version control system for the right time to run the commands you decide on, and will often take care of the different environments for you. As an example, if you needed to make a change to an open-source project hosted on GitHub, you would be able to clone the repository. You would then have a complete copy of it on your own computer, including all of its history. You then make the change you need...