In truth, the latest release of matplotlib sets a flag on show to
prevent repeated calls from doing any real damage.
But for classroom use, I suggest you just put "interactive : True" in
your rc file and then you have no need for show. Is there a downside
to this approach?
It seems that show() hangs if no figure has been created before calling (under matplotlib 0.62.4). Am I wrong or is it an unexpected use of show() ?