Legends and Colors
Legends
Legends are needed when you plot multiple series. McKinney is clear about one gotcha
here: passing label="..."label="..." to plot()plot() doesn’t draw a legend by itself — you must
still call ax.legend()ax.legend() afterwards, whether or not you set labels beforehand.
flowchart LR A["ax.plot(x, y1, label='square')"] --> C["ax.legend()"] B["ax.plot(x, y2, label='linear')"] --> C C --> D["Legend box appears, one entry per label"]
Legend
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y1 = [1, 4, 9, 16, 25]
y2 = [1, 2, 3, 4, 5]
plt.figure(figsize=(7, 4))
plt.plot(x, y1, label="square")
plt.plot(x, y2, label="linear")
plt.title("Two series")
plt.xlabel("x")
plt.ylabel("y")
plt.legend()
plt.tight_layout()
plt.show()Legend
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y1 = [1, 4, 9, 16, 25]
y2 = [1, 2, 3, 4, 5]
plt.figure(figsize=(7, 4))
plt.plot(x, y1, label="square")
plt.plot(x, y2, label="linear")
plt.title("Two series")
plt.xlabel("x")
plt.ylabel("y")
plt.legend()
plt.tight_layout()
plt.show()Colors
Use:
- high-contrast colors
- colorblind-friendly palettes when possible
- consistent color meaning across charts
Custom color
import matplotlib.pyplot as plt
plt.figure(figsize=(7, 4))
plt.plot([1, 2, 3], [3, 2, 5], color="#1f77b4")
plt.title("Custom color")
plt.tight_layout()
plt.show()Custom color
import matplotlib.pyplot as plt
plt.figure(figsize=(7, 4))
plt.plot([1, 2, 3], [3, 2, 5], color="#1f77b4")
plt.title("Custom color")
plt.tight_layout()
plt.show()Tip
Avoid using too many colors in one chart.
Next
Continue to Saving Plots as Images to export your finished, labelled charts.
🧪 Try It Yourself
Exercise 1 – Label a series and show the legend
Exercise 2 – Use a hex color code
Exercise 3 – Hide a series from the legend
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