After importing the module, the data is presented in step 2 from the How to do it… section in a convenient way, which will likely be similar to the way the data was originally stored.

Because of the way matplotlib works, it requires an X component as well as a Y component. In this case, our X component is just a sequence of integers, as many as data points. We create that in POS. In VALUES, we store the numeric value of the sales as a sequence, and in LABELS the associated label for each data point. All that preparation work is done in step 3.

Step 4 creates the bar graph, with the sequences X (POS) and Y (VALUES). These define our bars. To specify the period it refers to, we put labels on the x axis for each value with .xticks in the same way. To clarify the meaning, we add a label with .ylabel.

To display the resulting  graph, step 5 calls .show, which opens a new window with the result.