Matplotlib is a plotting library written in Python that supports creation of bar plots. By default, the bars in such a plot are filled with colors with no hatching pattern.
To set a hatching pattern assign it to the named argument hatch in the call to pyplot.bar():
matplotlib.pyplot.bar( ..., hatch="/" )
The list of all supported hatching patterns and their usage can be found here.
Tried with: Matplotlib 1.2, Python 3.2.3 and Windows 7 x64