import, functions, and threading

[Ian Bicking]

aahz at pythoncraft.com (Aahz) wrote in message news:<c2rkgj$irh$1 at panix2.panix.com>...
> There were some posts recently discussing whether it's poor style to put
> import statements inside functions.  I recently got reminded that there's
> one very good reason to avoid it: Python has an import lock that blocks
> more than one thread from executing import statements.  Putting import
> statements inside functions that might be called in a threaded
> environment is asking for deadlock trouble.

Just saw this on the week Python URL... anyway, an alternative that
should be safer:

somemodule = None

def whatever():
    global somemodule
    if somemodule is None:
        import somemodule

I'm still not sure if it's entirely safe in all cases, but I think it
is...?  Anyway, it allows for lazy loading.