1. Import matplotlib:

>>> import matplotlib.pyplot as plt

2. Prepare the data to be displayed on the graph and split it into different arrays:

>>> DATA = (
...    ('Q1 2017', 100),
...    ('Q2 2017', 150),
...    ('Q3 2017', 125),
...    ('Q4 2017', 175),
... )
>>> POS = list(range(len(DATA)))
>>> VALUES = [value for label, value in DATA]
>>> LABELS = [label for label, value in DATA]

3. Create a bar graph with the data:

>>> plt.bar(POS, VALUES)
>>> plt.xticks(POS, LABELS)
>>> plt.ylabel('Sales')

4. Save the graph to the hard drive:

>>> plt.savefig('data.png')