import keyword behaviour - performance impact if used multiple times?

[neophyte]

Nick Coghlan wrote:
>  > Is
>  > this something to do with system modules being singletons?
>
> They aren't singletons in the GoF design pattern sense. However,
Python's import
> machinery operates in such a way that it takes effort to get multiple
version of
> the same module into memory at the same time (it *can* be done, but
you have to
> work at it).
Given that this is exactly what I want, how can you do it?