To be able to code more than the most basic WLST scripts for WebLogic you should have reasonably good Python skills. Fortunately there are many good and free resources to get started.  Note that WLST as of WLS 12.1.2 is using Python 2.

Here is a list of recommendations to learn more Python and become better a WLST:

• A gentle Python video tutorial by MIT Open Courseware (better suited for the non-developers): Core Elements of a (Python) Program.
• Python Standard Library
• Maybe the best single source: free Jython book.
• Learn from the pros and check out the beautifully crafted scripts at Middleware Magic.
• I’ve done a 15 min WLST / JMX video. In depth WLST without any coding: overview.

As you can see I haven’t mentioned any real books yet. Let me know your favourite!