Matplotlib is a very powerful tool for making graphs in Python.  No graphing utility would be complete without allowing customization of each line on a graph.  As is common with Matplotlib and Python, modifying how your lines look is both easy and powerful. 

When using the plot function, it is as simple as passing in a two character string which specifies what kind of line it will be (or if it should just be markers), and what color.  Here is an example of a graph which uses red circles as markers with no line.

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plot(x_series, y_series, 'ro')

The first character in the string represents the color; the second represents the shape of marker or style of line used.  The following tables show a mapping of allowable colors and characters.

Here is another example, this time showing a full python script.

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#set up matplotlib and a new figure
import matplotlib.pyplot as plt
plt.figure()
 
#create data
x_series = [0,1,2,3,4,5]
y_series_1 = [x**2 for x in x_series]
y_series_2 = [x**3 for x in x_series]
 
plt.plot(x_series, y_series_1, 'r-')
plt.plot(x_series, y_series_2, 'c--')
plt.savefig("example.png")