Question: I've opened a project with the following structure in VS Code (1.71.0 on macOS, Intel) and activated a Dev Container (I've tried the default Python 3.9 and 3.10 containers from Microsoft, with and without using python3 -m venv ...): project/ .devcontainer/ devcontainer.json Dockerfile foo/ foo/ tests/ test_bar.py <-- IDE reports import error in this file resources/ __init__.py bar.py setup.py  In VS Code's terminal window, I can successfully run test_bar.py from directory project/foo with: python3 -m unittest discover foo/tests -p 'test_*.py'  So the project is valid and runs OK from the command line. But when I open file project/foo/foo/tests/test_bar.py in VS Code, I see the error Unable to import 'foo' pylint(import-error) underlined in red for the following line: from foo import bar  I see similar supposed errors for external packages I've installed with pip3 install. I've tried to inform VS Code by adding various relative and absolute paths (e.g. /workspaces/project/foo) to various places in project/.devcontainer.json, such as at:  customizations.vscode.settings  python.analysis.extraPaths python.autoComplete.extraPaths python.testing.unittestargs    But I've had no luck so far (after many IDE restarts and container image rebuilds). So I'm left wondering; how should one fix such IDE-flagged import errors in VS Code when using a Dev Container? Additional Info As a file was requested in the comments, here are the key test project files I used (I've not fixed any paths; my last test project was named vscode-python-dev-container, not project, which I used as shorthand above). devcontainer.json (with the containerEnv section added for the suggested PYTHONPATH change): // For format details, see https://aka.ms/devcontainer.json. For config options, see the README at: // https://github.com/microsoft/vscode-dev-containers/tree/v0.245.2/containers/python-3 { "name": "Python 3", "build": { "dockerfile": "Dockerfile", "context": "..", "args": { // Update 'VARIANT' to pick a Python version: 3, 3.10, 3.9, 3.8, 3.7, 3.6 // Append -bullseye or -buster to pin to an OS version. // Use -bullseye variants on local on arm64/Apple Silicon. "VARIANT": "3.10-bullseye", // Options "NODE_VERSION": "lts/*" } }, "containerEnv": { "PYTHONPATH": "/workspaces/vscode-python-dev-container/foo" }, // Configure tool-specific properties. "customizations": { // Configure properties specific to VS Code. "vscode": { // Set *default* container specific settings.json values on container create. "settings": { "python.defaultInterpreterPath": "/usr/local/bin/python", "python.linting.enabled": true, "python.linting.pylintEnabled": true, "python.formatting.autopep8Path": "/usr/local/py-utils/bin/autopep8", "python.formatting.blackPath": "/usr/local/py-utils/bin/black", "python.formatting.yapfPath": "/usr/local/py-utils/bin/yapf", "python.linting.banditPath": "/usr/local/py-utils/bin/bandit", "python.linting.flake8Path": "/usr/local/py-utils/bin/flake8", "python.linting.mypyPath": "/usr/local/py-utils/bin/mypy", "python.linting.pycodestylePath": "/usr/local/py-utils/bin/pycodestyle", "python.linting.pydocstylePath": "/usr/local/py-utils/bin/pydocstyle", "python.linting.pylintPath": "/usr/local/py-utils/bin/pylint" }, // Add the IDs of extensions you want installed when the container is created. "extensions": [ "ms-python.python", "ms-python.vscode-pylance" ] } }, // Use 'forwardPorts' to make a list of ports inside the container available locally. // "forwardPorts": [], // Use 'postCreateCommand' to run commands after the container is created. // "postCreateCommand": "pip3 install --user -r requirements.txt", // Comment out to connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root. "remoteUser": "vscode" }  Dockerfile: # See here for image contents: https://github.com/microsoft/vscode-dev-containers/tree/v0.245.2/containers/python-3/.devcontainer/base.Dockerfile # [Choice] Python version (use -bullseye variants on local arm64/Apple Silicon): 3, 3.10, 3.9, 3.8, 3.7, 3.6, 3-bullseye, 3.10-bullseye, 3.9-bullseye, 3.8-bullseye, 3.7-bullseye, 3.6-bullseye, 3-buster, 3.10-buster, 3.9-buster, 3.8-buster, 3.7-buster, 3.6-buster ARG VARIANT="3.10-bullseye" FROM mcr.microsoft.com/vscode/devcontainers/python:0-${VARIANT} # [Choice] Node.js version: none, lts/*, 16, 14, 12, 10 ARG NODE_VERSION="none" RUN if [ "${NODE_VERSION}" != "none" ]; then su vscode -c "umask 0002 && . /usr/local/share/nvm/nvm.sh && nvm install ${NODE_VERSION} 2>&1"; fi # [Optional] If your pip requirements rarely change, uncomment this section to add them to the image. # COPY requirements.txt /tmp/pip-tmp/ # RUN pip3 --disable-pip-version-check --no-cache-dir install -r /tmp/pip-tmp/requirements.txt \ # && rm -rf /tmp/pip-tmp # [Optional] Uncomment this section to install additional OS packages. # RUN apt-get update && export DEBIAN_FRONTEND=noninteractive \ # && apt-get -y install --no-install-recommends <your-package-list-here> # [Optional] Uncomment this line to install global node packages. # RUN su vscode -c "source /usr/local/share/nvm/nvm.sh && npm install -g <your-package-here>" 2>&1  bar.py: """An example module.""" JSON_STR = '{"a": 1}'  test_bar.py: """An example test.""" import json import unittest import requests # test external lib access from foo import bar class TestFooBar(unittest.TestCase): """An example test class.""" a = requests.__name__ # to eliminate warning above that package isn't used def test_foo_bar_json(self): """An example test.""" data = json.loads(bar.JSON_STR) self.assertEqual(data['a'], 1) 

Answer: I often have this same issue with Python+Devcontainer. What works for me is:  setting this env variable: export PYTHONPATH=/workspace, you can also try with /workspaces or /yourProjectName depending on your setup.  restart the Python Language Server with Ctrl+Shift+P > Python: Restart Language Server.   Note that you do not need to rebuild the container. When you find the correct value for PYTHONPATH, you can add it to your Devcontainer configuration.