Depending on the WSGI gateway/server, exceptions are handled differently but most of the time exceptions go to stderr or the error log.
Since this is not the best debugging environment Werkzeug provides a WSGI middleware that renders nice debugging tracebacks, optionally with an AJAX based debugger (which allows to execute code in the context of the traceback's frames).
from myapplication import application from werkzeug import DebuggedApplication, run_simple application = DebuggedApplication(application, evalex=True) run_simple('localhost', 4000, application)
This code spawns a Debugging Server on localhost:4000 with the debugger enabled. If you set evalex to False, the debugger is disabled.
Don't ever use the debugging middleware in a production environment since it can leak internal information that is part of the variable debug table. Even worse is a debugger with enabled evalex feature that can be used to execute code on the server!