Testing the availability of a module

[Peter Hansen]

Bo Peng wrote:
> Is there a better way than doing
> 
> try:
>    import aModule
> except:
>    has_aModule = False
> else:
>    has_aModule = True
> 
> The main concern here is that loading aModule is unnecessary (and may 
> take time).

Loading a module does *not* take time after the first time.  All it does 
is pull a reference out of sys.modules.  Are you worried about doing the 
above multiple times and wasting time?  Don't... you'll never notice it.

(And if you aren't doing the above multiple times, then you *really* 
shouldn't be worried about the time to load "aModule", unless you have 
reason to believe merely loading it takes an incredibly long time, in 
which case it is probably poorly designed as most modules should not be 
doing real work just by being imported.)

-Peter