ModuleNotFoundError: No module named

Linux

1. python3 -m pip install module-name
2. If using system Python: sudo apt install python3-module-name
3. Or create a venv: python3 -m venv .venv && source .venv/bin/activate

macOS

1. python3 -m pip install module-name
2. If Homebrew Python: ensure /opt/homebrew/bin is in PATH
3. pyenv users: pyenv rehash after installing packages

Windows

1. py -m pip install module-name
2. If multiple Python versions: py -3.11 -m pip install module-name
3. Check PATH: where python should show your expected Python

• If pip install succeeds but import still fails → Run python -c "import sys; print(sys.executable)" to confirm pip and python point to the same installation
• If Works in terminal but fails in IDE → Check IDE Python interpreter setting — it may point to a different environment
• If Error only in deployed/production environment → Ensure requirements.txt is complete: pip freeze > requirements.txt and redeploy

• Module name differs from pip package name (e.g., import cv2 but pip install opencv-python)
• Jupyter notebook using a different kernel than your terminal — run !pip install inside the notebook to match
• Namespace packages (no __init__.py) can cause this in Python 3.3+ if the directory structure is wrong

# Check which python is running
python3 -c "import sys; print(sys.executable)"
# /usr/bin/python3

# Check which pip is installing to
python3 -m pip --version
# pip 23.1 from /usr/lib/python3/dist-packages/pip

# Always use python3 -m pip to guarantee match
python3 -m pip install requests