ImportError: No module named 'mpl_toolkits'

ImportError: No module named ‘mpl_toolkits’

$ python -c "import mpl_toolkits.mplot3d"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: No module named 'mpl_toolkits'

Why this happens

Your environment doesn’t have Matplotlib fully installed (partial install, broken venv), or a local module shadows mpl_toolkits.

Fix

Reinstall Matplotlib and its dependencies; avoid naming local files mpl_toolkits.py.

Wrong code

from mpl_toolkits.mplot3d import Axes3D
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')

Fixed code

# Ensure matplotlib is installed
# pip install matplotlib
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D  # provided with Matplotlib
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
plt.show()