[Python-Dev] Re: Future division detection (original) (raw)

Skip Montanaro skip@pobox.com (Skip Montanaro)
Mon, 05 Nov 2001 17:29:51 +0100 

Christopher> What I would like to do is have a function that can check
Christopher> to see if the CO_FUTURE_DIVISION flag is set and if it is
Christopher> and the denominator is 1 then return the numerator, else
Christopher> return the rational.

Yeah, you can do this. It's just a little awkward.

% python
Python 2.2b1+ (#9, Oct 29 2001, 14:53:15) 
[GCC 2.96 20000731 (Linux-Mandrake 8.0 2.96-0.48mdk)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from __future__ import division
>>> def f():
...   pass
... 
>>> f.func_code.co_flags
8195
>>> 
% python
Python 2.2b1+ (#9, Oct 29 2001, 14:53:15) 
[GCC 2.96 20000731 (Linux-Mandrake 8.0 2.96-0.48mdk)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> def f():
...   pass
... 
>>> f.func_code.co_flags
3

Note how the code object's co_flags field changed. I think you just need to & it with 2<<12. During import you could have something like this:

def _junk():
  pass
future_div = not not (_junk.func_code.co_flags & (2<<12))
del _junk

then test the value of future_div where you need it.

-- Skip Montanaro (skip@pobox.com) http://www.mojam.com/ http://www.musi-cal.com/

P.S. I hope I guessed right about demangling your email address. If so, I've just exposed it to all the little email harvesting gremlins. So sorry... ;-)