Do you like reading code written by other developers?
Reading the code written by other programmers makes you a better developer. If you are an average developer, start reading code written by great programmers to improve your coding skills.
From quite some time, I am realising the importance of reading code. Whenever I was stuck in some task during development, reading the source code of library solves the problem. This also helps when the documentation of the library you are using does not answer you questions. What you should do? The answer is simple open the code of the library, read the relevant part of code and the problem is solved. You may also read the term "Source code never lies".
We are lucky as most of the popular projects these days are open source. Reading code of good Open Source projects takes your programming skills to the next level. I am grateful to all great developers who open source their code for the benefit of all. The simple API provided by popular open source projects to developers, have some great code behind it.
Reading Open source code can also make you an Open Source contributor.
While reading the source code of an Open Source project, you may find some section of code that could be implemented in a much better way. Great, it's time to pay back to the Open Source world. Read the contributing guidelines of the project and submit Pull request. isn't it great.
What are you waiting for? Take a cup of coffee, find an Open Source project of your interest like flask and start spending some great time reading its code.