This Matplotlib Bars lesson is for a beginner. Read the short notes, run each example, then change one name or number and run it again.
A bar chart compares categories. The height of each bar is the value, and the label is the category name.
Sort the categories only when the order itself means something, such as a ranking.
Example 1: Start here
plt.bar(topics, counts) draws one bar per topic.
topics = ["Python", "SQL", "Git"] # a list; the values stay in this order
counts = [18, 11, 7] # a list; the values stay in this order
print(list(zip(topics, counts))) # zip keeps each pair together
Example 2: List the points
Matplotlib Bars draws points. Printing each pair lets you check the data before a chart library plots it.
points = [(1, 20), (2, 12), (3, 18)] # a list; the values stay in this order
for x, y in points: # repeat the indented lines once per value
print(x, y) # a comma prints each value, with a space between
Example 3: Find the highest bar
The tallest bar is the largest number. max does that lookup.
heights = [20, 12, 18] # a list; the values stay in this order
print(max(heights)) # the largest value
Example 4: Label each point
A chart label belongs with its number. zip keeps each day next to its height.
labels = ["Mon", "Tue", "Wed"] # a list; the values stay in this order
heights = [20, 12, 18] # a list; the values stay in this order
for label, height in zip(labels, heights): # repeat the indented lines once per value
print(label, height) # a comma prints each value, with a space between
plt.bar(topics, counts) draws one bar per topic.
