ctrl-C behaviour

I should add that iPython is in so many other ways a shining example of how to implement a really great command line interface. All the tab completion, docstring tricks, etc, etc, are all great.

Sorry, I hadn't noticed this ticket was open.

Are you using ipython with one of the threading flags (-wthread, -qthread, -gthread or -pylab)? If so, there is unfortunately nothing I can do, since Python has no mechanism for asynchronous, cross-thread exceptions.

With a normal ipython (no thread support), I don't see this behavior. On my laptop, hitting Ctrl-C immediately does cancel the line I was on and gives me a new prompt:

In [1]: line to be cancelled...
KeyboardInterrupt

In [1]: print 'all ok'
all ok

If you are seeing problems and you are not using the threading flags, please:

• Update to ipython SVN to see if that helps.

• If it doesn't, please give me more details about your OS, python version, etc.

Closing: I don't see this behavior and no more info is forthcoming from original submitter.

Reopen with the information requested above if necessary. Keep in mind the note about the problem not being fixable in the threaded shells, due to fundamental OS/Python limitations about multiple threads and signal handlers.

Hi there

Didn't receive any notification until this last message, for some reason.

I am seeing this problem with IPython 0.7.2. You are right in thinking that it only occurs in the presence of a threading module; in this case '-pylab'. There *may* still something that could be done for that case though: where the "Press enter to continue" prompt is shown, it would be good if another press of ctrl-C would clear that warning. At present, ctrl-C just causes that warning to appear again. Can you trap the ctrl-C keypress at that prompt? This would be a cosmetic thing that would help usability quite a bit for pylab users.

Cheers JP

No, the problem is that when threads are present, I can't trap the signals at all in the thread where user code is running.

Furthermore, in a line-oriented program (such as ipython), there is no way to clear a previously written line. Something like that can be done if running in a GUI, or even using curses in a terminal, but not in a purely line-driven program, since the state of previous lines is gone once they've been printed.

It's a bummer, and this is the main reason why I continue to use Tk as my pylab backend (it doesn't need threads because python manages its mainloop in a single thread). But basically, python, multiple threads and asynchronous signals are kind of a toxic mix. I've read a LOT of discussions over the years on this problem, and repeatedly all I get from core python developers is that there really isn't much that can be done in this context.

I'm always on the lookout for new ideas, so if you know of a possible solution for this problem, I'd be delighted to try it out. But believe me, the current situation isn't sub-optimal for lack of trying, unfortunately.

Closing: as of 0.8.0, we do have support for Ctrl-C in the presence of threads. Finally!