modulenotfounderror: no module named 'cv2'

Not specified by the original author.

How to fix ModuleNotFoundError: No module named 'cv2'

The pip name is opencv-python, the import name is cv2; install with python -m pip install opencv-python. If it is 'already installed', you are in the wrong environment: check that python and pip point at the same env, or you named a file cv2.py that is shadowing the real one.

The exact error

ModuleNotFoundError: No module named 'cv2'

Fix it

1. python -m pip install opencv-python Expected: Successfully installed

2. python -c "import cv2; print(cv2.__version__)" Expected: prints a version

3. Still failing? python -m pip show opencv-python vs which python: make pip and python match; rename any cv2.py in your project. Expected: consistent env, no shadowing

When this applies

import cv2 -> No module named 'cv2'

When this does NOT apply

cv2 imports but crashes on libGL (different error, different fix)

Versions

any

Why it happens

pip name vs import name mismatch, or interpreter/env mismatch.

Edge cases

Jupyter: restart the kernel after installing; notebook pip can target a different env.

Asked about: ModuleNotFoundError: No module named 'cv2' (gh:madboy2026/vcamera (setup troubleshooting)). The verified fix: The pip name is opencv-python, the import name is cv2; install with python -m pip install opencv-python. If it is 'already installed', you are in the wrong environment: check that python and pip point at the same env, or you named a file cv2.py that is shadowing the real one. Full thread: https://github.com/madboy2026/vcamera/blob/HEAD/tests/SETUP.md

Not specified by the original author.

TL;DR

For "ModuleNotFoundError: No module named 'langchain_openai'": run pip show langchain-openai. LangChain splits every provider into its own package. pip install langchain never includes them. A fresh venv, a new container, or a lockfile that dropped the extra is the usual trigger. ` pip install -U langchain-openai 3. uv-managed project? Use uv add langchain-openai.

ModuleNotFoundError: No module named 'langchain_openai'

When to use

You are seeing this: If it prints nothing, the package is genuinely absent. Use this skill when you run into "Diagnose: ModuleNotFoundError: No module named 'langchain_openai'".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Steps

1. Run pip show langchain-openai. If it prints nothing, the package is genuinely absent. Also check you are in the right environment: which python and pip list | grep langchain should agree.
2. LangChain splits every provider into its own package. pip install langchain never includes them. A fresh venv, a new container, or a lockfile that dropped the extra is the usual trigger.

pip install -U langchain-openai

3. uv-managed project? Use uv add langchain-openai. Do not mix pip and uv.

from langchain_openai import ChatOpenAI
print("ok")

4. If the import works, done. If pip claims it installed but the import still fails, you have two environments and installed into the wrong one.

Why this happens

LangChain splits every provider into its own package. pip install langchain never includes them.

Edge cases

• Also check you are in the right environment: which python and pip list | grep langchain should agree.

Diagnostic procedure grounded in the official install docs, verified 2026-09-26. Install: docsgchain.com/oss/python/langchain/install

Not specified by the original author.

ModuleNotFoundError: No module named 'OpenSSL'

TL;DR: the distribution is called pyOpenSSL but the module is OpenSSL. Run pip install pyOpenSSL and the import works.

ModuleNotFoundError: No module named 'OpenSSL'

The fix

pip install pyOpenSSL

Verify:

python -c "from OpenSSL import SSL; print('ok')"

Expected output: ok.

Agent? Search Vectle for more: curl -s 'https://vectle.com/api/v1/search?q=pyOpenSSL+No+module+named+OpenSSL'

When this applies

• from OpenSSL import SSL fails on a fresh virtualenv, container, or CI runner.
• You ran pip install OpenSSL (no such distribution) or never installed it.
• urllib3 1.x PyOpenSSL injection code that imports OpenSSL.

When it does NOT apply

• module 'lib' has no attribute 'X509_V_FLAG_CB_ISSUER_CHECK', which is the pyOpenSSL/cryptography version mismatch.
• Import errors for _cffi_backend, which is the cffi backend problem.

Why this happens

Distribution names and import names are independent on PyPI, and pyOpenSSL is one of the classic mismatches. pip cannot guess from the import statement, so the ModuleNotFoundError persists until you learn the real distribution name. The PyPI page always lists the exact install command.

Compatibility

pyOpenSSL 23+. Needs the cryptography package, which pip installs automatically.

The module is OpenSSL but the distribution is pyOpenSSL, so guessing the pip name from the import fails. The pyOpenSSL project page documents pip install pyOpenSSL as the install command. This is the same distribution-name versus import-name mismatch as python-jose and Flask-Bcrypt, and the fix is the same one-line install.