ModuleNotFoundError: No module named '...'

When Python raises ModuleNotFoundError: No module named '...', it means the import statement cannot find the requested module anywhere in the module search path.

What It Means

Python looks for modules in sys.path — a list of directories that includes the script’s directory, the standard library, and site-packages. If the module isn’t in any of these locations, this error is raised.

Why It Happens

• The module isn’t installed (pip install needed)
• You’re in the wrong virtual environment (or none at all)
• The module is installed for a different Python version (e.g. Python 2 vs 3)
• The script is running from a directory that shadows the module name
• A custom script has the same name as the module you’re trying to import

How to Fix It

Step 1: Install the missing module

pip install <module-name>

For specific versions:

pip install <module-name>==1.2.3

Step 2: Activate your virtual environment

If you created a virtual environment but forgot to activate it:

# On Linux/macOS:
source venv/bin/activate

# On Windows:
venv\Scripts\activate

Step 3: Check Python version compatibility

Some modules only support certain Python versions:

# Check which Python you're using
python --version

# Install for your specific Python version
python3.11 -m pip install <module-name>

Step 4: Inspect the module search path

import sys
print(sys.path)

Make sure the directory containing your module appears in this list.

Step 5: Rename conflicting scripts

If you named your script the same as the module (e.g. requests.py), rename it — Python will import your script instead of the real module.