Certification is a great way to show your employers and/or customers that you are highly skilled at programming a particular language. In addition, it is a great way to motivate you to continuously learn.
The Python Institute is offering a way to certify your understanding of the python programming language. Testing is done through Pearson Vue. It is very likely that Pearson Vue has a testing center near you. They have testing centers all over the U.S. Use the links in this post to learn more and schedule a certification test near you.
Take a look at the exam objectives and exam syllabus at the Python Institute website. If you do not understand the some of the concepts presented, then that is where you should start your research. Begin using those concepts in your code. I think the best way to prepare is to use the python programming language. If you have the opportunity to use it at work, that is great. Otherwise, there are lots of home projects that you can use to learn. Here are some ideas:
There is a python package called PyQt that allows developers to create complex graphical user interfaces. There is also PyGtk for creating user interfaces with Gtk and wxPython for creating user interfaces with wxWidgets.
Find out what interests you, and start your own project to learn python.