34. 2D Contour & Filled Contour Plots (contourf)

Contour plots visualize 3D scalar fields $Z = f(X, Y)$ on a 2D page by drawing lines of constant value (isolines), identical to geographic elevation maps or weather pressure maps.

Mental Model Intuition

Topographical hiking map showing mountain elevation rings.

Core Concepts & Mechanics

`levels` ParameterResolution

`levels=10` creates 10 discrete elevation bands. Passing an explicit list `levels=[-1, -0.5, 0, 0.5, 1]` specifies exact threshold values.

Higher level counts produce smoother gradient fills.

plt.contourf(X, Y, Z, levels=20, cmap='plasma')

Common Beginner Mistakes & Pro Fixes

Avoid the top errors and bad plotting practices that trip up new Python developers

Troubleshooting

Quick Lesson Takeaways

`plt.contour()` draws isolines of constant value.
`plt.contourf()` draws filled color bands between isolines.
`plt.clabel()` stamps numerical elevation values onto lines.

Topic 34 • Python IDE

Python 3.12 • Matplotlib

Presets:

Ctrl + Enter to run

Run Python code to inspect terminal output.

Real-World Datasets (1-Click Switcher)

Switch from abstract numbers to relatable Cricket, Cinema & Business charts

5 Curated Datasets

Hands-on Challenge: Draw a Contour Plot

+50 XP

Write Matplotlib code to solve the objective and see your live plot render

Objective Instructions:

Create meshgrid for `x=np.linspace(-2, 2, 30)`, `y=np.linspace(-2, 2, 30)`, compute `Z = X**2 + Y**2`, and draw `plt.contourf(X, Y, Z, cmap='plasma')`.

Required Keywords:✓ contourf✓ meshgrid

Challenge Code Editor

Challenge Output GraphLive Vector Preview

Write code on the left to render live challenge plot

End of Lesson Knowledge Check

Quick Mini Quiz: 2 Concept Questions

Test your understanding to unlock the lesson completion badge

Which Matplotlib function is used to create a standard continuous 2D line plot?

What must you call after specifying label='...' so that the legend actually appears on the canvas?

0 of 2 answered

Heatmaps & Matrix Display with imshow()

Next Lesson

Spines Customization & Centered Axes