__import__ .vs. sys.modules

[holger krekel]

Fran?ois Pinard wrote:
> Hello, people.
> 
> Yesterday, someone suggested on this list that:
> 
>         module = sys.modules[__name__]
> 
> should best be written:
> 
>         module = __import__(__name__)

Yesterday i was thinking that '__name__' refers
to the usual preset __name__ from python inside
a module. And this should not have a dot if i am not
mistaken.

For example the 'os.path' module is explicitely bound
by the os-module with 'sys.modules['os.path']=...' 
(just have a look in the source).

> This looked nice to me, at first.  However, if `__name__' contains dots,
> only the first of the above writing works.  The second could be made to
> work by splitting `__name__' at periods and doing more stunts after that,
> but then, it becomes heavier and does not seem worth all the trouble.

So yes, if you have some variable containing any 
(possibly dotted) module name than 

    module = sys.modules[somestring] 

is the general approach. Note that using this approach 
the module must be already loaded. 

__import__ can handle the case with dotted modulenames as well
(lookup the docs for this extended usage) but it would automatically
try to load the modules.

regards,

    holger