How to do it...

The following code draws a bar plot:

1. Set up data for the x and y axes:

month_num = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
units_sold = [500, 600, 750, 900, 1100, 1050, 1000, 950, 800, 700, 
              550, 450]

2. Allocate the space and specify the layout of the figure:

fig, ax = plt.subplots()

3. Set the descriptive month names as x axis ticks:

plt.xticks(month_num, calendar.month_name[1:13], rotation=20)

4. Plot the bar graph:

plot = ax.bar(month_num, units_sold)

5. Add the data value to the head of the bar:

for rect in plot:
    height = rect.get_height()
    ax.text(rect.get_x() + rect.get_width()/2., 1.002*height,'%d' % 
    int(height), ha='center', va='bottom')

6. Display the graph on the screen:

plt.show()