sympy/sympy — pull request #2140 by hacman (2013-05-29 04:11:46+00:00)
Title: moving imports of numpy (and matplotlib/mpl_toolkits) out of module scope...

...and into functions/classes

reduces the import time of sympy by 50-75%.

See discussion at https://code.google.com/p/sympy/issues/detail?id=3427