[IPython-dev] Should IPython be a singleton?

[Brian Granger]

Thanks! I will have a look at this to see how it differs from what I have
been doing.

Brian

On Wed, Aug 26, 2009 at 4:27 PM, Robert Kern <robert.kern at gmail.com> wrote:

> On 2009-08-26 18:17 PM, Brian Granger wrote:
> >
> >     When tracking down problems like this, one thing you have to be very
> >     careful
> >     about is not creating references via your instrumentation. It's
> >     disturbingly
> >     easy to do. :-)
> >
> >
> > Yes, it is very tough to do right.
> >
> >     __builtins__.__IPYTHON__ and __builtins__.__IPYTHON__active are two
> >     culprits,
> >     and the remaining one is a cell object. I'm not sure where he is
> >     coming from.
> >
> >
> > In my version, I have gotten rid of __IPYTHON__ and IPYTHON_active is an
> > int.
> >
> > What is a cell object?
>
> It is created when there are closures.
>
> http://docs.python.org/c-api/cell.html
>
> > Could I see the foo.py script?
>
> Oops! Sorry. I thought I catted it. Here it is with a few more things
> cleaned up.
>
> [~]$ cat foo.py
> import gc
> import sys
> import types
>
> from IPython.core.shell import InteractiveShell
>
> real_main = sys.modules['__main__']
>
> s = InteractiveShell('foo')
> print s
>
> # Clean up.
> del s.shell
> del s
> del __builtins__.__IPYTHON__active
> del __builtins__.__IPYTHON__
> if hasattr(sys, 'ipcompleter'):
>     del sys.ipcompleter
> sys.stdin = sys.__stdin__
> sys.stdout = sys.__stdout__
> sys.stderr = sys.__stderr__
> sys.displayhook = sys.__displayhook__
> sys.excepthook = sys.__excepthook__
> sys.modules['__main__'] = real_main
>
> for obj in gc.get_objects():
>     if getattr(type(obj), '__name__', None) == 'InteractiveShell':
>         print obj
>         refs = gc.get_referrers(obj)
>         print '%s references:' % len(refs)
>         for ref in refs:
>             print type(ref)
>             if isinstance(ref, dict):
>                 print 'A dict with keys: %r' % (ref.keys(),)
>             elif isinstance(ref, list):
>                 print 'A list of %s elements; probably gc.get_objects().' %
> len(ref)
>             elif type(ref).__name__ == 'cell':
>                 print 'A cell: %r' % ref
>                 print ref.cell_contents
>             else:
>                 print ref
>             print
>
>
> --
> Robert Kern
>
> "I have come to believe that the whole world is an enigma, a harmless
> enigma
>  that is made terrible by our own mad attempt to interpret it as though it
> had
>  an underlying truth."
>   -- Umberto Eco
>
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