On Thu, 2009-02-19 at 00:43 +0100, Nicolas Steinmetz wrote:
[...]
> The issue is that engine in engine(request.POST['search'], 10) does not
> become google(request.POST['search'], 10) in the case where the user
> chosed "google" as engine.
>
> Is there a solution or did I have to test all values with a if or case
> loops ?
Two solutions spring to mind. The problem you are trying to solve is:
given a string naming a function, call that function. So you have to map
the string name to the function object.
Method #1: use the globals() dictionary to look up the function object.
globals()[engine](....)
The drawback here is that you should still sanitise the contents of
"engine", since otherwise the POST data could be used to call anything
in your globals() namespace. That could be a denial-of-service attack,
at a minimum (a security exploit at worst).
Method #2: create a dictionary mapping "engine" values to the right
callable.
try:
{'google': google,
'yahoo': yahoo,
# ...
}[engine](...)
except KeyError:
# Engine name is not valid. Handle appropriately here.
The drawback is the percieved redundancy between the string name and the
function name. Still, I would prefer this solution. It automatically
only allows "permitted" value through -- and if, say, you wanted to
temporariliy disable the yahoo functionality, you would just comment out
or remove that line from the dictionary. It also means you don't *have*
to call your functions by the same name as the search engine, which
would be useful if you ever included an engine whose name was not a
valid Python identifier, for example.
By the way, this second pattern is more-or-less idiomatic Python for a
C-style switch-statement. Usually preferable to a series of if...elif...
statements, particularly for a large number of choices.
Regards,
Malcolm
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