On Mon, 2007-07-30 at 12:53 +0000, André wrote: > On Jul 30, 9:39 am, Neil Cerutti <[EMAIL PROTECTED]> wrote: > > On 2007-07-30, Steven D'Aprano > > > > <[EMAIL PROTECTED]> wrote: > > > How would one tell at runtime if a particular feature has been > > > enabled by the "from __future__ import thing" statement? > > > > I don't understand the qualification, "at runtime," you're > > making. What's wrong with just importing what you want and using > > it? If it's already been enabled, no harm will come from the > > import statement. > > > > I'm not the OP, so perhaps I am missing his intent. However, I can see > a good reason for asking this question. > > I seem to recall that the "from __future__ import" statement can only > be done at the beginning of a script.
Incorrect. It must be done at the beginning of the *file*. > What if you are designing a > module meant to be imported, and used by other programs over which you > have no control? You can't use "from __future__ import" in your > module. Incorrect. You can use a __future__ import in a module as long as you do it at the beginning of the modul file. > So, you may have to find a way to figure out what's been > done. (the example given with the division operator is a good one). No. __future__ directives are scoped to the module. Observe: $ cat f1.py def f1(): print 1/2 f1() import f2 f2.f2() $ cat f2.py from __future__ import division def f2(): print 1/2 $ python f1.py 0 0.5 As you can see, f1 uses past semantics, f2 uses future semantics. Just use whatever __future__ directives you need for your module at the beginning of your module, and everything will just work. HTH, -- Carsten Haese http://informixdb.sourceforge.net -- http://mail.python.org/mailman/listinfo/python-list
