Labels, Titles & Legends

Matplotlib is a Python library for creating charts and visualizations — but a chart without labels is a puzzle, so this lesson is about making every plot explain itself.

Learn Labels, Titles & Legends in our free Matplotlib course — a beginner-friendly interactive lesson with worked examples, a practice exercise and a quick…

Part of the free Matplotlib course at LearnCodingFast — hands-on lessons with examples you run in your browser, plus practice exercises and a quick quiz.

You'll add axis labels and a title, attach a legend that names each line, and position that legend exactly where you want it.

Three calls turn an anonymous chart into a clear one: plt.xlabel() , plt.ylabel() , and plt.title() . Add them any time before plt.show() .

What you'll see: a rising line, now with "Month" written under the x-axis, "Sales (units)" rotated along the y-axis, and a bold "Monthly Sales" heading centered above the chart.

When a chart has several lines, a legend tells the reader which is which. Give each line a label= , then call plt.legend() once.

What you'll see: two lines — Online climbing and In-store falling — with a small legend box in a corner that maps each color to its name, plus the axis labels and title from before.

By default Matplotlib drops the legend wherever it fits, but you can place it precisely with the loc argument — for example 'upper left' or 'lower right' .

What you'll see: the steep "Squares" curve and the gentler "Doubles" line, with the legend box anchored firmly in the top-left corner instead of floating wherever Matplotlib chooses.

Replace each ___ to fully label this chart and show a legend.

You called plt.legend() but never passed label= to your plots. Add a label to each line.

Add your labels and legend before plt.show() . Once the figure is shown it is cleared.

Plot two lines and add axis labels, a title, and a positioned legend.

Lesson 4 complete — your charts explain themselves!

You added axis labels and titles, named your lines, and placed a legend exactly where you wanted it.

🚀 Up next: Markers, Line Styles & Colors — control exactly how each line looks.

Practice quiz

Which call labels the horizontal axis?

  • plt.axis('x')
  • plt.xname()
  • plt.xlabel('text')
  • plt.labelx()

Answer: plt.xlabel('text'). plt.xlabel('text') sets the label under the x-axis.

Which call labels the vertical axis?

  • plt.ylabel('text')
  • plt.axisy('text')
  • plt.labely('text')
  • plt.yname('text')

Answer: plt.ylabel('text'). plt.ylabel('text') sets the label along the y-axis.

Which call adds a heading above the chart?

  • plt.heading('text')
  • plt.caption('text')
  • plt.header('text')
  • plt.title('text')

Answer: plt.title('text'). plt.title('text') draws a heading above the plot.

How do you give a line a name for the legend?

  • plt.name('Sales')
  • Pass label='Sales' to plt.plot
  • plt.legend('Sales')
  • plt.tag('Sales')

Answer: Pass label='Sales' to plt.plot. Pass label= to each plot call, e.g. plt.plot(x, y, label='Sales').

Which call actually displays the legend box?

  • plt.showlegend()
  • plt.key()
  • plt.legend()
  • plt.labels()

Answer: plt.legend(). plt.legend() draws the legend listing every labelled line.

What does plt.legend(loc='upper left') do?

  • Pins the legend to the upper-left corner
  • Hides the legend
  • Adds a second legend
  • Removes the labels

Answer: Pins the legend to the upper-left corner. The loc argument positions the legend, here in the upper-left corner.

Why might plt.legend() show nothing and warn 'No artists with labels'?

  • The title is missing
  • The figure is too small
  • show() was already called
  • None of the plotted lines were given a label=

Answer: None of the plotted lines were given a label=. legend() only lists artists that have a label; without labels it warns and shows nothing.

What does loc='best' do?

  • Doubles the legend size
  • Lets Matplotlib pick the least-crowded corner
  • Disables the legend
  • Moves the legend off-screen

Answer: Lets Matplotlib pick the least-crowded corner. loc='best' asks Matplotlib to choose the least-crowded location automatically.

When must labels and legend be added relative to plt.show()?

  • After show()
  • It does not matter
  • Before show(), since show clears the figure
  • Only inside a loop

Answer: Before show(), since show clears the figure. Add labels and the legend before show(); once shown, the figure is cleared.

Which loc value places the legend in the bottom-right corner?

  • loc='top right'
  • loc='bottom'
  • loc='right bottom'
  • loc='lower right'

Answer: loc='lower right'. loc='lower right' anchors the legend to the bottom-right corner.