Matplotlib is a plotting library written in Python that can be used to create line plots. By default, all the values are drawn with no marker symbol.
To set a marker assign it to the named argument marker in the call to pyplot.plot():
matplotlib.pyplot.plot( ..., marker="^" )
The list of all supported line styles and their usage can be found here.
Tried with: Matplotlib 1.2, Python 3.2.3 and Windows 7 x64