a simple def how-to

[vsoler]

On 7 mar, 16:23, Andreas Waldenburger <use... at geekmail.INVALID> wrote:
> On Sun, 7 Mar 2010 07:05:26 -0800 (PST) vsoler
>
>
>
> <vicente.so... at gmail.com> wrote:
> > Hello,
>
> > My script starts like this:
>
> > book=readFromExcelRange('book')
> > house=readFromExcelRange('house')
> > table=readFromExcelRange('table')
> > read=readFromExcelRange('read')
> > ...
>
> > But I would like to have something equivalent, like...
>
> > ranges=['book','house','table','read']
> > for i in ranges:
> >     var[i]=readFromExcelRange(i)
>
> > which does not work. I assume I should be using globals() instead of
> > var, but I do not know how to write my script.
>
> > Can anybody help?
>
> One additional line, and it works (all the following code is untested,
> I might have goofed it up somewhere, but you get the idea):
>
> ranges=['book','house','table','read']
> var = {}
> for i in ranges:
>     var[i]=readFromExcelRange(i)
>
> Or, more succinctly:
>
> var = dict((i, readFromExcelRange(i)) for i in ranges)
>
> although that looks a bit crowded. Perhaps
>
> rd = readFromExcelRange
> var = dict((i, rd(i)) for i in ranges)
>
> looks better, but not by much, IMO.
>
> In Python 3 you can also just say
>
> var = {i:readFromExcelRange(i) for i in ranges}
>
> (I think. I don't have Python 3.) This looks comparatively neat,
> because there are no nesting parens.
>
> And just in case you think it's a good idea to meddle with globals and
> create actual "variables": it's not. You absolutely want dictionaries
> here. It's basically a bad idea to create names *implicitly* that
> you're going to use *explicitly*. (That is, it is in Python anyway,
> because it does not provide a clean and clear way of doing this. Other
> languages might provide that sort of thing, and it might be awesome,
> but in Python, no sir.)
>
> /W
>
> --
> INVALID? DE!

Thank you Andreas.

Your comprehensive answer makes a lot of sense to me.