Debugging

Pdb

• pdb is the integrated (but quite unhandy) debugger

• To start it at a specific code point

import pdb; pdb.set_trace()

• l to list the current code, p to print a variable, n for next statement, s to step-into and b for breakpoint

• use the power of dir() to get a list of attributes of a variable / class

Pudb

• Nice ncurses based debugger

• Same keybindings as pdb

• Install

pip install pudb

• Afterwards edit /usr/lib/python2.6/site-packages/urwid/raw_display.py, go to signal_init and signal_restore, comment out all code and insert pass

• To invoke pudb

import pudb; pudb.set_trace()

• To start a script in pudb

python -m pudb.run yourfile.py

Winpdb

• A graphical debugger with remote support and conditional breakpoints

• To invoke it

import rpdb2; rpdb2.start_embedded_debugger("password")

• Now launch winpdb File –> Password, File –> Attach

• To tunnel winpdb through SSH

ssh -C -N -f -L 51000:localhost:51000 user@$SERVER_HOST

Inject a pudb into a running process

• Install pyrasite

• Create a inject-pudb.py file

import pudb;pudb.set_trace()

• Find pid of desired python process

• Inject the code

pyrasite <pid> inject-pudb.py

Connect an ipython shell to a running process

• Install pyrasite

• Create a inject-ipython.py file

from IPython.frontend.terminal.embed import InteractiveShellEmbed
ipshell = InteractiveShellEmbed()
ipshell()

• Find pid of desired python process

• Inject the code

pyrasite <pid> inject-ipython.py