importing down in code rather than at top of file.

[dieter]

Tobiah <toby at tobiah.org> writes:

> Is it  worth while to defer the import of a large module that seldom
> gets used in the script?
>
>
> 	import sys
> 	import os
>
> 	if hardly_ever_happens():
> 		
> 		import large_module
> 		large_module.do_task()

I have used delayed import for different reasons:

 * to avoid cyclical imports

 * to avoid import deadlocks in multi-tasking programs
   (Python 2 (at least) used to protect the import machinery with
   a lock; which under some conditions could lead to deadlocks
   in a multi-tasking program).

Typically, the delayed import was then in a function - relying
on the fact that importing an already imported module is fast
(thus, we do not lose much even if the function is called multiple times).