Where to place imports

Diez B. Roggisch deets at nospam.web.de
Fri Jan 23 19:04:42 CET 2009


Steve Holden schrieb:
> Diez B. Roggisch wrote:
> [...]
>> The only valid reason for doing imports inside functions is if you
>> otherwise get into circular dependency hell, or have modules that need
>> some manipulation of the sys.path before they actually can be imported.
>> This is never true for system modules, and certainly to avoid if possible.
>>
> Well there is also the somewhat obscure point that an import of specific
> names inside a function makes them local, which *might* make a
> performance difference with tight loop nesting inside - though obviously
> the need for such will best be determined by benchmarking:

But that could be mitigated using aliasing, which is a more general 
optimization technique, as it works not only for imported names but also 
for e.g. bound methods, or any other chained lookups.

Diez



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