在每个页面上运行函数的最佳方法

I have one question, namely, what is the best way to run any function on each python application in the project? For example, I have 1 project - bbCms which contains 2 apps - articles and board. And I would like to run function doSomething on each page of these apps. On PHP I can create file, e.g. functions.php, type code and inside each app by require run this function. I have one question, namely, what is the best w