ModuleNotFoundError: No module named '…'

Python raises ModuleNotFoundError: No module named 'x' when the interpreter running your code cannot find module x on its import path. Almost always the package is either not installed, or installed for a different interpreter or virtual environment.

Reproduce the error

python -c "import requests"

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

The process exits with status 1 and the traceback names the missing module.

Check which interpreter runs your code

Install packages with the same interpreter that runs the code. python -m pip guarantees that, while a bare pip may belong to another Python on PATH.

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

Both lines must point inside the same environment (the active virtual environment, or the system installation).

Check whether a module is importable without importing it

importlib.util.find_spec returns None when a module cannot be found, which is useful in scripts and health checks.

python -c "import importlib.util as u; print(u.find_spec('json') is not None, u.find_spec('requests') is not None)"

True False

Fix

1. Install into the interpreter you run: python -m pip install requests.
2. In a virtual environment, activate it first (source .venv/bin/activate on Linux and macOS, .venv\Scripts\activate on Windows), or run .venv/bin/python directly.
3. Use the import name, not the distribution name. Common mismatches:

FAQ