imports happen once

gistfile1.py

>>> import time
>>> def time_it(fun):
...     start = time.time()
...     fun()
...     end = time.time()
...     print 'Time:', end - start
... 
>>> def foo():
...     import logging
...     import multiprocessing
...     import thread
... 
>>> def bar():
...     import logging
...     import multiprocessing
...     import thread
... 
>>> time_it(foo)
Time: 0.0508568286896
>>> time_it(foo)
Time: 1.4066696167e-05
>>> time_it(foo)
Time: 1.28746032715e-05
>>> time_it(foo)
Time: 1.28746032715e-05
>>> time_it(bar)
Time: 1.31130218506e-05
>>> time_it(bar)
Time: 1.28746032715e-05
>>> time_it(bar)
Time: 1.28746032715e-05