Python "ModuleNotFoundError: No module named ...": How to Fix It

Traceback (most recent call last):
  File "app.py", line 1, in <module>
    import requests
ModuleNotFoundError: No module named 'requests'

Python looked for a module called requests and couldn't find it in any of the places it searches. Nine times out of ten, the package is installed — just not in the Python that's running your code.

Cause 1: it isn't installed

The simple case. Install it:

python -m pip install requests

Using python -m pip (rather than plain pip) guarantees you install into the same Python you'll run with. On many Macs and Linux systems the command is python3.

If the project has a requirements.txt, install everything at once:

python -m pip install -r requirements.txt

(requirements.txt explained)

Cause 2: wrong environment (the most common)

You have more than one Python: the system one, one from Homebrew or the Microsoft Store, and probably a virtual environment for this project. You installed the package into one and are running another. (Python virtual environments)

Check which Python is running and which pip installs where:

python -c "import sys; print(sys.executable)"
python -m pip --version

Activate the project's virtual environment

source .venv/bin/activate     # macOS / Linux
.venv\Scripts\activate        # Windows

Your prompt shows (.venv) when it's active. Then install and run again.

Your editor uses a different interpreter

VS Code picks a Python interpreter per workspace. If running from the terminal works but the editor's Run button fails (or the reverse), open the Command Palette → Python: Select Interpreter and choose the project's .venv. (VS Code for beginners)

Jupyter uses a different kernel

In a notebook, install into the kernel's environment:

%pip install requests

Cause 3: the install name differs from the import name

Some packages are installed under one name and imported under another:

import	pip install
cv2	opencv-python
PIL	pillow
sklearn	scikit-learn
yaml	pyyaml
bs4	beautifulsoup4
dotenv	python-dotenv

pip install cv2 fails or installs the wrong thing. Look up the correct package name.

Be careful with AI-suggested package names too — models sometimes invent plausible-sounding packages, and attackers register those names. Check the package exists and is the real one before installing. (AI hallucinated packages)

Cause 4: it's your own module

ModuleNotFoundError: No module named 'utils'

when utils.py is in your project. Python finds your own modules based on where you run from, not where the file is.

• Run from the project root: python -m app.main rather than cd app && python main.py.
• Make sure folders that are packages are importable (a folder of modules imported as app.utils should be inside the directory you run from).
• Avoid naming your files after real packages — a file called requests.py or email.py shadows the real one and causes confusing errors.

(File paths explained)

Cause 5: it works locally but not on the server

The server's environment doesn't have the package because it wasn't in requirements.txt. Freeze what you've installed:

python -m pip freeze > requirements.txt

…or better, add packages explicitly as you go. (Works locally but not in production)

And if pip itself refuses

On newer Linux and Homebrew Pythons, pip install outside a virtual environment fails with externally-managed-environment. That's a nudge to use a virtual environment. (Fix it)

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EasySpawn runs your Python app in a consistent environment on its own server, with dependencies installed from your requirements on every deploy. See how it works or join the waitlist.

Related: Python Virtual Environments · requirements.txt Explained · pip "externally-managed-environment" · What Is Python?