programmatically define a new variable on the fly
bruno.42.desthuilliers at wtf.websiteburo.oops.com
Fri Aug 10 12:10:53 CEST 2007
Lee Sander a écrit :
> I would like to define a new variable which is not predefined by me.
> For example,
> I want to create an array called "X%s" where "%s" is to be determined
> based on the data I am processing. So, for example, if I the file
> I'm reading has
> g 99
> on the first line, I want to create a new variable called "Xg" whose
> is 99.
> I tried eval("Xg=*99") but that did not work.
> any help would be greatly appreciated
As others already pointed out, the canonical solution is to use a dict,
and it's almost always the best solution - a variant being to use an
object (eventually a module object) and dynamically add attributes to it
Now, for the corner case where you *really* want to dynamically create
new names in the module itself, the solution is to use exec. But I would
definitively *not* recommand this solution unless you really know what
you're doing and why you're doing it.
For the record, I did use this last solution twice in seven years. And
it was mostly to avoid repeating boilerplate code in some low-level
module of a framework. Definitively not a common case...
 which, FWIW, doesn't make much differences since attributes are
stored in dicts....
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