ModuleNotFoundError: No module named 'x'
Python 3
ModuleNotFoundError: No module named 'requests' (or another package).
What it means (root cause)
The import name is not installed in the interpreter you are running, or you are executing with a different environment than the one where pip installed it (a venv/conda mismatch).
The symptom developers actually see: ModuleNotFoundError: No module named 'requests' (or another package).
Step-by-step fix
Concrete, ordered steps from the dataset. Apply them in order; each line is a verified action, not generic advice.
- 1Confirm which interpreter runs: which python / where python and sys.executable inside the script.
- 2Install into that environment: python -m pip install <name> (the -m ensures the active interpreter).
- 3If using a venv, activate it first so pip and python point at the same environment.
Where this error appears
Languages, frameworks, and runtimes where this error is observed (from the 2026 DevFixPro error dataset, retrieved 2026-08-29):
Python 3 (all versions). Almost always an environment/venv mismatch, not a code bug.
How to prevent it & common questions
Practical prevention plus the questions developers ask most about this error.
What does "ModuleNotFoundError: No module named 'x'" mean?
The import name is not installed in the interpreter you are running, or you are executing with a different environment than the one where pip installed it (a venv/conda mismatch).
Which environments are affected by ModuleNotFoundError: No module named 'x'?
Python 3
How do I fix ModuleNotFoundError: No module named 'x'?
Confirm which interpreter runs: which python / where python and sys.executable inside the script. Install into that environment: python -m pip install <name> (the -m ensures the active interpreter). If using a venv, activate it first so pip and python point at the same environment.
How do I prevent ModuleNotFoundError: No module named 'x'?
Activate the venv before install and run; pin dependencies in requirements.txt so the environment is reproducible.
pip installed it but import still fails?
You installed into one interpreter and run with another (common with venvs/conda). Use python -m pip install so pip and python match, and activate the venv first.
Where does Python look for modules?
sys.path — the script's directory, then PYTHONPATH, then the active environment's site-packages. Print sys.path to see what is actually searched.
Related DevFixPro tools
Real, browser-only utilities on DevFixPro that help while you work through this issue. These are navigation aids, not a substitute for the fix above.
Sources & attribution
- Error records aggregated from Google Search Console query gaps (2026-05-21~2026-08-18) for devfixpro.com, plus official framework docs (MDN, Node.js docs, Python docs, Go.dev, Rust book, Oracle Java docs, Docker docs, npm docs). Source dataset retrieved 2026-08-29. License: CC BY 4.0 — attribute DevFixPro (devfixpro.com).
- Official reference: https://docs.python.org/3/tutorial/modules.html
- All cause, environment, fix and prevention text on this page is taken verbatim from the DevFixPro 2026 error dataset. DevFixPro does not invent root causes or fixes.
How this ModuleNotFoundError: No module named 'x' page is built
Each error page is generated from a single record in the DevFixPro 2026 error dataset. The meaning, root cause, environments, fix steps, prevention, and official references are copied verbatim from that dataset and its official-doc sources; related-error links are computed from the error's category and explicit peer list. No root cause or fix is invented. The retrieval date for this dataset is 2026-08-29.