How to step through Python code to help debug issues?

python

debugging

pdb

ide

byAnton Shumikhin·Feb 21, 2025

Debug your way through complex Python code using the built-in pdb debugger. Drop pdb.set_trace() - a debugging spree spark plug - into the scripts where issues may lurk. This halts the code, now you're in an interactive detective hormone-infused session, to investigate the case with commands like n (next line), s (step into), p (print variable), and c (continue running). Here's a peak to pique you:

def buggy_function(x):
    # This is where we'll start our bug-hunting safari
    import pdb; pdb.set_trace()
    # Is "x + y" a mathematical marvel or a dreadful disaster? Let pdb guide the way
    return x + y # Oops, maybe y needs an existence check

buggy_function(10) # Calling all detectives - here begins a mysterious numeric adventure!

Mastering various debugging environments

IDEs like PyCharm, VS Code, and Thonny furnish user-friendly GUI debuggers for your service, featuring variable watchers, expression evaluators, and more.

If you are a "terminalphile", relish the command-line charm of pdb or unbox the extended package of ipdb. This buffed-out debugger merges syntax highlighting, better tracebacks, auto-completion and enjoys a camaraderie with IPython capabilities.

Unlocking handy debugging tips

Debugging in the wild

Rare code species thrive in inaccessible environments like a remote server or a Docker container. Employ remote debugging tools like PyCharm Professional, debugpy/ptvsd (VS Code) to corner those elusive bugs.

Post-mortem puzzle

After the infernal crash comes the divine enlightenment; Use pdb.post_mortem() after a Scriptural Apocalypse, Did I just wax lyrical? Nah, that's simply an exception!

Quick triggers with `sys.breakpointhook`

If Python 3.7+ looms large at your coding vista, invoke the debugger expeditiously with the breakpoint() function. Channel its high-spirited behavior through 'sys.breakpointhook' or enter the "PANDORA'S BOX VARIABLE" - PYTHONBREAKPOINT.

Async Code Antics

Asynchronous programming ups the ante with its async/await constructs, To allay your sanity from this asynchronous pandemonium, seek the wisdom of IDE debuggers or the a command in pdb.

Conquering complex debug landscapes

Harnessing the power of breakpoints

Breakpoints aren't just runtime napping points; they are strategic signposts for logging insights or evaluating conditions on-the-move.

Tracing through recursion

Recursive functions? More fun! Use the l (list code), u (go up) and d (go down) command trifecta to wander through the layers of recursion in pdb.