matplotlib is a pure python plotting library designed to bring
publication quality plotting to python with a syntax familiar to
matlab users.  A lot progress towards this goal has been made since
the first release of matplotlib, the library does produce high quality
2D plots.  All of the plotting commands can be accessed either via a
functional interface familiar to matlab users or an object oriented
interface familiar to python users, and several high resolution output
formats are supported.

Tutorial: http://matplotlib.sourceforge.net/tutorial.html