Not the OP, but I program professionally in Python for the past 5 years and i have never set a breakpoint. Assuming they don't work in lambdas (sounds like a tooling issue), is this really such a big problem?
This means you are either one of the best or one of the worst programmers. People in the middle have bugs in their program and can use a debugger to find them.
>sounds like a tooling issue
The tool, in this case, being the interpreter. Which is exactly the point.