Temporarily entering the debugger in IPython

Question

In IPython, with %pdb enabled, I can hit Ctrl-C and be dropped to a Python debugger console at the exact point I stopped the program.

However, at this point the program is entirely stopped, and I can't resume he execution even if I run continue in the debugger.

Is IPython able to do that, then let me resume the execution of the program when I'm done?

Note: I know about pdb.set_trace(), but this is not what I'm looking for. I'm looking for a way to quickly, temporarily stop IPython for quick harmless checks instead of having to manually add set_trace in my code, if possible.

Answer 1

I can hit Ctrl-C and be dropped to a Python debugger console at the exact
point I stopped the program.

Ctrl-C is interrupting your program, which raise a KeyboardInterrupt, when you resume with continue you continue ...and interrupt your program as asked by the Ctrl-C you sent. Ctrl-C is not to "pause" the program in debug mode at one certain point.

What you are looking for is to set a breakpoint a one particular line, like %run -d allow you to do. See %run?.

Answer 2

There are a lot of corner cases with this type of thing. However adding a signal handler to your usercustomize.py gets you quite far:

cat >> $(python -m site --user-site)/usercustomize.py <<EOF
import signal, pdb
signal.signal(signal.SIGINT, lambda *args: pdb.set_trace())
EOF

Now when you launch python, you will get that signal handler installed.

For example, you can now interrupt the SimpleHTTPServer:

$ python -m SimpleHTTPServer
Serving HTTP on 0.0.0.0 port 8000 ...
^C--Return--
> [...].local/lib/python2.7/site-packages/usercustomize.py(3)<lambda>()>None
-> signal.signal(signal.SIGINT, lambda *args: pdb.set_trace())
(Pdb) locals()
{'__return__': None, 'args': (2, <frame object at 0x10245b238>), 'os': <module 'os' from '[...]/lib/python2.7/os.pyc'>}