How to Fix ModuleNotFoundError in Python

Error message: ModuleNotFoundError: No module named 'xyz'

Python raises ModuleNotFoundError when an import statement cannot find the requested module. This is one of the most common errors beginners encounter.

What Causes It

1. The package isn’t installed — most common cause
2. Wrong Python environment — you installed in one virtualenv but run in another
3. Circular imports — two modules try to import each other
4. PYTHONPATH is misconfigured — Python can’t find your custom modules
5. The module name is misspelled — case-sensitive

Fix 1: Install the Missing Package

pip install requests

If it’s already installed, upgrade:

pip install --upgrade requests

For Python 3 specifically (when both Python 2 and 3 are installed):

pip3 install requests

Fix 2: Check Your Virtual Environment

If you’re using a virtual environment, activate it first:

# Create venv
python -m venv venv

# Activate (Linux/macOS)
source venv/bin/activate

# Activate (Windows)
venv\Scripts\activate

# Now install
pip install requests

Verify the module exists:

python -c "import requests; print(requests.__version__)"

Fix 3: Fix PYTHONPATH and Circular Imports

For custom modules, ensure Python can find them:

import sys
sys.path.append("/path/to/your/module")
import your_module

For circular imports, restructure your code. Instead of module_a importing module_b and vice versa, move the shared code to a third module:

# shared.py — common code both need
# module_a.py — imports from shared
# module_b.py — imports from shared

Prevention

• Always use virtual environments (python -m venv venv)
• Run pip list to verify installed packages
• Keep a requirements.txt: pip freeze > requirements.txt
• When activating a venv, check your terminal prompt shows (venv)
• For custom modules, use pip install -e . in the project root

Quick Checklist