[Matplotlib-users] Exact semantics of ion()??

What does ion() exactly do?  From reading the documentation, I gather that
the interactive mode is equivalent to issuing an automatic draw() after each
plotting comment.  However, a program like the following one does not draw
anything (Matplotlib 1.0, both on Mac OS X and Windows):

>>>
from matplotlib import pyplot as pp

pp.plot([10, 20, 50])
pp.draw()

raw_input('Press enter...')  # No graph displayed?!!
<<<

However, adding ion() and removing the draw() displays the graph.  So, it
looks like the interactive mode does more than what I gather from the docs. 
What does ion() do in addition to adding an automatic draw()?  Can the above
program be modified so as to draw the graph but without using ion()?

Any input would be much appreciated!

EOL

PS: the documentation I was referring to reads: "The interactive property of
the pyplot interface controls whether a figure canvas is drawn on every
pyplot command. If interactive is False, then the figure state is updated on
every plot command, but will only be drawn on explicit calls to draw(). When
interactive is True, then every pyplot command triggers a draw."
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