debugging notes with python

- with pdb, use aliases

# Ned's .pdbrc
# Print a dictionary, sorted. %1 is the dict, %2 is the prefix for the names.
alias p_ for k in sorted(%1.keys()): print "%s%-15s= %-80.80s" % ("%2",k,repr(%1[k]))
alias pi p_ %1.__dict__ %1. .. # instance variables of %1
alias ps pi self ............. # instance variables of self.
alias pl p_ locals() local: .. # Print the locals.
alias nl n;;l ................ # Next and list.
alias sl s;;l ................ # and step and list.
alias uu u;;u ................ # up the stack
alias dd d;;d ................ # down the stack

source : http://stackoverflow.com/a/1624037

- use sys hooks to react on exception

def traceit(frame, event, arg):
   if event == "line":
        lineno = frame.f_lineno
        print "line", lineno
   return traceit

def main():
    print "In main"
    for i in range(5):
        print i, i*3
    print "Done."

sys.settrace(traceit)
main()

source : http://www.dalkescientific.com/writings/diary/archive/2005/04/20/tracing_python_code.html

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# code snippet, to be included in 'sitecustomize.py' import sys def info(type, value, tb): if hasattr(sys, 'ps1') or not sys.stderr.isatty(): # we are in interactive mode or we don't have a tty-like # device, so we call the default hook sys.__excepthook__(type, value, tb) else: import traceback, pdb # we are NOT in interactive mode, print the exception... traceback.print_exception(type, value, tb) print # ...then start the debugger in post-mortem mode. pdb.pm() sys.excepthook = info

source : http://code.activestate.com/recipes/65287/

- simple logging 

import logging
logging.basicConfig(level=logging.DEBUG)
logging.debug('This is a debug message.')

source : http://aymanh.com/python-debugging-techniques#logging