How does CO_FUTURE_DIVISION compiler flag get propagated?

Terry twestley at gmail.com
Sat Jul 2 18:29:42 CEST 2011


I've built a Python app for the iPhone, http://www.sabonrai.com/PythonMath/.

Like embedding Python in another app, it uses PyRun_SimpleString() to
execute commands entered by the user. For evaluating expressions, it
uses PyEval_EvalCode() with the dictionary from the __main__ module.

Future division ("from __future__ import division") works within
scripts executed by import or execfile(). However, it does not work
when entered interactively in the interpreter like this:

>>> from __future__ import division
>>> a=2/3

You get classic (integer) division, but if you enter it as follows,
you get future (float) division.

>>> from __future__ import division;a=2/3

It appears that the CO_FUTURE_DIVISION compiler flag is not being
retained in the interpreter so that later commands get compiled
without that flag.

I found a hint in
http://groups.google.com/group/comp.lang.python/browse_thread/thread/13a90a9f6eb96c73/960e47f572a59711?lnk=gst&q=co_future_division#960e47f572a59711,
but I don't see that PyRun_SimpleStringFlags returns the flags it
uses. I guess I could watch for the user to enter the import command
but that's really brittle.

Thanks.



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