exec globals and locals

Quentin Lampin quentin.lampin at gmail.com
Wed Sep 2 22:20:49 CEST 2009


2009/9/2 Chris Rebert <clp2 at rebertia.com>

> On Wed, Sep 2, 2009 at 1:13 PM, Quentin Lampin<quentin.lampin at gmail.com>
> wrote:
> > 2009/9/2 Chris Rebert <clp2 at rebertia.com>
> >>
> >> On Wed, Sep 2, 2009 at 4:54 AM, Quentin Lampin<quentin.lampin at gmail.com
> >
> >> wrote:
> >> > Hi,
> >> > Being fairly new to Python, I'm trying to figure out the best way to
> use
> >> > the
> >> > exec statement and I must admit that I am a bit lost.
> >> >
> >> > Consider this case:
> >> > exec "print 'a'" in {},{}   [exp.1]
> >> > It means  that I'm (kindly) asking the interpreter to execute the code
> >> > string  "print 'a'" with empty globals and locals.
> >> > Considering that globals and locals are empty, I would expect [exp.1]
> to
> >> > raise an exception about 'print' not being known.
> >>
> >> In Python versions prior to 3.0, print is a statement (like for,
> >> while, if, etc), not a function (note how you don't need parentheses
> >> when using it); so it doesn't matter whether the built-in functions
> >> are available or not, print will still work.
> >>
> >> Cheers,
> >> Chris
> >> --
> >> http://blog.rebertia.com
> >
> > Ok, thanks for the explanation.
> > I'm really confused with print being a statement but it's seems that I
> won't
> > have to put too much effort on understanding why since 3.0 states the
> > contrary. :p
> > By the way, could you suggest me a link that explains why 3.0 changed
> this.
> > It might provide some material to understand the pros and cons of
> "function
> > statements".
>
> http://www.python.org/dev/peps/pep-3105/ (PEP 3105 -- Make print a
> function)
> http://mail.python.org/pipermail/python-dev/2005-September/056154.html
>
> Cheers,
> Chris
> --
> http://blog.rebertia.com
>


Thanks a lot Chris!
Quentin
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