Python ModuleNotFoundError: No module named

A plain-words explanation of this Python message: what it means, the usual causes, and the steps that fix it.

The messageModuleNotFoundError: No module named 'numpyy'

Make the error yourself

Run with Python 3.14.10. This is the smallest example we could find that shows it.

Python program (main.py)

import numpyy
print("loaded")

Output (the real message)

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

Why it happens

import searches the places Python knows for a module with that name. It found none. Typical reasons: the module is not installed (most third-party modules such as requests, numpy or pandas must be installed first), the name is misspelled (as in the example, numpyy), it is installed for a different Python than the one running your program, or you are in a virtual environment that does not contain it.

How to fix it

1. Check the spelling against the package page.
2. Install it with the same Python that runs the program: python -m pip install numpy (on some systems python3, or py -m pip install numpy on Windows).
3. If you use several Pythons or a virtual environment, activate the right one first and run python -m pip list to see what it has.
4. The name you import is not always the name you install: you install opencv-python but write import cv2.

The corrected version

Python program (main.py)

import json
print(json.dumps({"loaded": True}))

Output (the corrected version)

{"loaded": true}

How to avoid it

Keep a requirements.txt for each project and use one virtual environment per project, so that the program runs on any computer with the same install command.

Questions

This is an independent guide. It is not connected with Python, Microsoft, Google, GitHub or the Git project. Product names belong to their owners. Examples were run on 13 November 2026 in a practice folder or a blank workbook; your version may word a message slightly differently.