A surprising number of companies and services provide public APIs to access their data and services or interact with their application. This gives you, as a developer, a powerful set of tools to very simply build your own new apps and integrations. If you've learned some Python but aren't sure what to do next, then building small apps on public APIs is a great way to develop your skills further.
We'll go through the setup that most public APIs require, getting keys and using OAuth to access the APIs, hosting the app somewhere. We'll use a Slack bot as an example, plus some more examples with cool APIs. Lastly, we'll go through list of available APIs (and links to more lists) to get your creative juices flowing. You never knew that these services had an API.