Fooliery here with some new free bee's for the beginner python and pygame game developer.
Here is a group of modules to help keep time in your game. Inside is also a mp4 video tutorial on how to use it.
Makes it easy to say when to spawn an enemy, how long a level should last. set a event to happen in appropriate order.
Vary easy to understand and a great source to learn and build on.
Hope this helps out
Look over the source code. There is a few extra goodies inside.