python-debugpy

To debug a failing pytest test, run the specific test with the `--pdb` or `--trace` flag while disabling xdist. This drops you into an interactive pdb REPL at the failure point to inspect local state safely.

Remote debugging with debugpy uses the Debug Adapter Protocol (DAP) to attach to a running Python process, such as a gateway or subprocess. This allows you to inspect local variables and execution frames without stopping or restarting the system.

Yes, you can perform post-mortem inspection using `pdb.post_mortem` to analyze an unhandled Python exception. This opens an interactive REPL at the exact crash site to inspect local variables and understand what changed right before the failure.

The best way to diagnose a missing value in a Python data transformation is to insert a `breakpoint()` at the suspect line, reproduce the issue, and use pdb commands like `p`, `pp`, and `where` to trace how the program arrived at that state.

Interactive pdb debugging has known incompatibilities with pytest-xdist. To use pdb breakpoints or the `--pdb` flag correctly, you must disable xdist parallel execution to ensure safe handling and proper frame inspection.

Use debugpy attach instead of pdb when you cannot restart the process, such as when debugging long-lived gateway or subprocess execution. Debugpy lets you attach to the running process to inspect state, whereas pdb requires starting the script under its module.