Debuggers and property based testing. It is a select few people that can actually productively (not their own metrics) use print statements for debugging. Learning how to craft repro scenarios and adequately capturing state in a debugging session can enable junior devs to easily surpass senior devs.

Property based testing aren't quite formal methods, but I think they are a good stepping stone. And they also somewhat force your code into an algebraic/functional style which also make it amenable to refactoring, better testing and is easier to understand.

Design tools like Swagger can help one think through services w/o diving into code. Code itself is a liability and should be thought of as "spending" not creating. Code is a debt.

Refactoring and code understanding tools, if you use PyCharm (you should, it is free in all senses), learn how to navigate into your libraries. Read you libraries.