Python pdb-meetup-bcn

1. Introduction to the
Python debugger (pdb)
@raulcumplido

2. Usages of pdb
Invoked as a script
Post Mortem Mode
Run Mode
Trace Mode

3. Invoked as a script
Only
Python
~$ python -m pdb test.py
3.2+
~$ python -m pdb –c continue test.py
~$ python -i test.py

4. Post Mortem Mode
pdb.pm()

5. Post Mortem Mode
>>> import pdb
>>> import mymodule
>>> mymodule.test()
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "./mymodule.py", line 4, in test
test2()
File "./mymodule.py", line 3, in
test2
print spam
NameError: spam
>>> pdb.pm()
> ./mymodule.py(3)test2()
> -> print spam
(Pdb)

6. Run Mode
pdb.run(statement[, globals[, locals])
pdb.runeval(expression[globals[, locals])
pdb.runcall(function[, argument, ...])

7. Run Mode
>>> import pdb
>>> import mymodule
>>> pdb.run('mymodule.test()')
> <string>(0)?()
(Pdb) continue
NameError: 'spam'
> <string>(1)?()
(Pdb)

8. Trace Mode
pdb.set_trace()

9. Debugger tips
• Entering a blank line
repeats(except list)
• Commands not recognized are
executed
– When exception nothing
changes
• Support for aliases

10. Debugger commands
h(elp) [command]

11. Debugger commands
w(here)

12. Debugger commands
d(own)
u(p)

13. Debugger commands
s(tep)

14. Debugger commands
n(ext)

15. Debugger commands
unt(il)

16. Debugger commands
c(ont(inue))

17. Debugger commands
j(ump) lineno

18. Debugger commands
l(ist) [first[, last]]

19. Debugger commands
a(rgs)

20. Debugger commands
p expression
pp expression

21. Debugger commands
[!]statement

22. Debugger commands
q(uit)

23. Debug over the network or
to an existing process
http://dev.man-online.org/man1/rpdb2/
http://code.activestate.com/recipes/576515/
http://stackoverflow.com/questions/4163964/p
ython-is-it-possible-to-attach-a-console-
into-a-running-process
Attach to python using gdb 
$> gdb
(gdb) attach (pid)
Investigar si se puede hacer algo más con
esto
 Working on github on RPDB

24. We’re hiring!
Raúl Cumplido | @raulcumplido
raul@catchoom.com | +34 627566095
catchoom.com | @catchoom