[Python-Dev] a quit that actually quits (original) (raw)

Fernando Perez fperez.net at gmail.com
Fri Dec 30 06:53:50 CET 2005

Nick Coghlan wrote:

As Fernando pointed out, anything else means we'd be well on our way to re-inventing IPython (although I'd be interested to know if sys.inputhook would have made IPython easier to write).

[sorry if this drifts off-topic for python-dev. I'll try to provide useful info on interactive computing in python here, and will gladly answer further detailed discussion about ipython on the ipython-dev/user lists ]

In my case, I don't think it would have made that much of a difference in the end, though initially it might have been tempting to use it. IPython started as my private collection of sys.ps{1,2} + sys.displayhook hacks in $PYTHONSTARTUP. I then discovered LazyPython, which had a great sys.excepthook, and IPP, which was a full-blown derivative of code.InteractiveConsole. I decided to join all three projects, and thus was ipython born. Given that IPP was the 'architecture', from the moment we had what is still today's ipython, it was based on code.InteractiveConsole, and at that point I doubt that having sys.inputhook would have mattered.

Incidentally, just two days ago I removed the last connection to code.py: at this point I had overridden so many methods, that there was no point in keeping the inheritance relationship. All I had to do was copy two remaining methods, and the main ipython class became standalone (this frees me for ongoing redesign work, so it was worth doing it).

So in summary, while sys.inputhook would make it easy to do lightweight interactive customizations, if you really want a more sophisticated and featureful system, it probably won't matter.

Note that this is not an argument against sys.inputhook: exposing customizability here may indeed be useful. This will allow people to write, with minimal effort, systems which pre-process special syntaxes and ride on top of the python engine. IPython exposes the exact same thing as a customizable hook (called prefilter), and people have made some excellent use of this capability. The most notable one is SAGE:

http://modular.ucsd.edu/sage

a system for interactive mathematical computing (NSF funded). If anyone is in the San Diego area, the first SAGE meeting is in February:

http://modular.ucsd.edu/sage/days1/

and I'll be giving a talk there about ipython, including some of its design and my plans for a more ambitious system for interactive computing (including distributed computing) based on Python. The prototypes of what we've done so far are briefly described here (the first was funded by Google as a summer of code project):

http://ipython.scipy.org/misc/ipython-notebooks-scipy05.pdf http://ipython.scipy.org/misc/scipy05-parallel.pdf

I hope this is of some use and interest.

Regards,

f

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