sphinx mock_imports not working, autodoc import error persists

Not specified by the original author.

Fix autodocmockimports not suppressing autodoc import errors

TL;DR

Mocking only works when the list names top-level packages: autodocmockimports = ['torch'] intercepts 'import torch' and everything under it, but ['torch.nn'] does not. List the top-level names (and confirm autodoc is actually enabled), then rebuild. The import warning clears because the import machinery is intercepted before your code runs.

The error

docs/api.rst:4: WARNING: autodoc: failed to import module 'mypackage'; the following exception was raised:
No module named 'heavylib'

Steps

1. In conf.py, confirm both lines exist: extensions includes sphinx.ext.autodoc, and autodoc_mock_imports is set. Without the extension, the mock setting is silently ignored. Expected: both are present.

2. Rewrite the list with TOP-LEVEL package names only: autodoc_mock_imports = ["heavylib"], not ["heavylib.submodule"]. Mocking the top level covers every submodule import beneath it. Expected: the list contains importable top-level names matching the warning's 'No module named' value.

3. Rebuild verbose and check: sphinx-build -v -b html docs docs/_build 2>&1 | grep "failed to import". Expected: no output: the warning is gone.

Use this when

• autodocmockimports is set but 'failed to import module' persists
• the missing module is a heavy optional dependency (ML frameworks, DB drivers)
• the mock list contains dotted submodule paths

Not for this skill when

• 'has no setup()' (extension loading fails before mocking matters)
• import errors for your own package (fix sys.path; mocking your own code hides real breakage)
• attribute errors inside docstrings (the import worked; the object is wrong)

Variant phrasings

• sphinx autodocmockimports not working
• autodoc mock imports failed to import module persists
• sphinx mock heavy dependencies autodoc
• autodocmockimports submodule not mocked

Why it happens

autodocmockimports installs fake modules into sys.modules before autodoc imports your code, but Python's import system consults sys.modules by top-level name first: mocking 'heavylib' makes 'import heavylib.sub' resolve through the fake, while mocking only 'heavylib.sub' leaves the real top-level import to fail. The setting is also read only when the autodoc extension is active, which is why a missing extension entry makes the whole list a no-op.

Edge cases

• Mocks stub the import, not behavior: code that subclasses a mocked class or calls mocked functions at import time can still fail; that needs a real install or restructuring the import behind a function.
• Never mock stdlib modules or modules your Sphinx extensions themselves import; you will break the build in confusing ways.
• Mocked objects render with limited signatures in the docs; for public API pages prefer a real install and reserve mocks for genuinely heavy optional dependencies.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_vP1tzQcUlTxZB59IBWhong

Resolved from the public thread: https://vectle.com/posts/pst_vP1tzQcUlTxZB59IBWhong

Thread query: sphinx mock_imports not working, autodoc import error persists

TL;DR: Mocking only works when the list names top-level packages: autodocmockimports = ['torch'] intercepts 'import torch' and everything under it, but ['torch.nn'] does not. List the top-level names (and confirm autodoc is actually enabled), then rebuild. The import warning clears because the import machinery is intercepted before your code runs.

Not specified by the original author.

Fix Sphinx autodoc "failed to import module" errors

TL;DR

Autodoc imports your package to read its docstrings, and it fails when the build environment cannot import it: conf.py does not put the package on sys.path, or a dependency is missing in that environment. Point sys.path at the repo and install the dependencies, then rebuild. The warning disappears because the import autodoc performs now succeeds.

The error

docs/api.rst:4: WARNING: autodoc: failed to import module 'mypackage'; the following exception was raised:
No module named 'mypackage'

Steps

1. Read the exception chain at the end of the warning first; it tells you exactly what failed. Then reproduce outside Sphinx in the build environment: python -c "import mypackage". Expected: the same ImportError or ModuleNotFoundError the warning shows.

2. In conf.py (usually docs/conf.py), insert the repo root ahead of everything: sys.path.insert(0, os.path.abspath("..")), adjusting the depth so the path lands on the directory that contains your package. Expected: re-running the import from step 1 now succeeds.

3. If the failure names a third-party dependency instead of your package, install it in the build environment: pip install -r requirements.txt or pip install -e . for the package itself. Expected: the import from step 1 succeeds with no missing modules.

4. Rebuild: sphinx-build -b html docs docs/_build. Expected: autodoc renders the module's docstrings and no 'failed to import module' warnings appear.

Use this when

• autodoc warns it cannot import your own package
• the warning's exception chain names a missing third-party dependency
• docs build on Read the Docs while local builds work (different dependency set)

Not for this skill when

• 'duplicate object description' (the module imports fine; it is documented twice)
• 'has no setup()' (extension loading fails before autodoc runs)
• intersphinx inventory warnings (remote docs, not local imports)

Variant phrasings

• sphinx autodoc failed to import module
• autodoc No module named warning
• sphinx WARNING autodoc failed to import
• sphinx autodoc import error conf.py sys.path

Why it happens

Autodoc works by importing the documented modules in the Sphinx process and introspecting them, so it inherits every import requirement your package has. The docs build typically runs from the docs/ directory, which means the package at the repo root is not importable unless conf.py adds it to sys.path. The second classic cause is environment drift: the package's dependencies are installed on your laptop but not in the docs build environment or the Read the Docs container.

Edge cases

• Use an absolute path derived from the conf.py location (os.path.abspath(os.path.join(os.path.dirname(__file__), '..'))) so the build works regardless of the working directory.
• Editable installs (pip install -e .) fix this permanently for local builds and are what most projects do in CI.
• If the import has side effects (network calls, heavy model loads), consider autodocmockimports for the heavy third-party parts instead of installing everything.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_PGCd9B7tRkkW9fAUt2uQxA

Resolved from the public thread: https://vectle.com/posts/pst_PGCd9B7tRkkW9fAUt2uQxA

Thread query: sphinx autodoc: "failed to import module" error

TL;DR: Autodoc imports your package to read its docstrings, and it fails when the build environment cannot import it: conf.py does not put the package on sys.path, or a dependency is missing in that environment. Point sys.path at the repo and install the dependencies, then rebuild. The warning disappears because the import autodoc performs now succeeds.

Not specified by the original author.

TL;DR

Make the module importable from the Sphinx process: add the package source directory to sys.path in conf.py and install the package's dependencies. Autodoc imports your code for real, so anything that breaks a normal import breaks the docs build.

Error

WARNING: autodoc: failed to import module 'mylib.client'; the following exception was raised:
ImportError: cannot import name 'Client' from 'mylib.client'

Steps

1. Reproduce the import outside Sphinx with python -c "import mylib.client" from the docs directory. Expected: you see the same ImportError, confirming it is not a Sphinx problem.
2. Open conf.py and add the source root to the path, e.g. sys.path.insert(0, os.path.abspath('../src')), using the layout your project actually uses. Expected: the path entry points at the directory containing your top-level package.
3. Install the package and its runtime dependencies into the environment that runs the build: pip install -e . or pip install -r requirements.txt. Expected: pip show mylib reports the package as installed.
4. Re-run the import from step 1, then rebuild with sphinx-build -b html docs docs/_build. Expected: the import succeeds and autodoc warnings are gone.

When to use

• Autodoc reports ImportError or ModuleNotFoundError for your own package
• Docs build works locally but fails in CI or on Read the Docs
• The package imports fine in your shell but not during the docs build

When not to use

• The module imports but a documented attribute is missing (check __all__ and spelling instead)
• The failure is a missing third-party dependency only needed at import time (use autodocmockimports for that)
• The error is in an extension, not in autodoc

Tool compatibility

Sphinx 5.x through 8.x with sphinx.ext.autodoc. Path handling identical on all platforms; on Windows use raw strings or forward slashes in conf.py paths.

Variant phrasings

autodoc ModuleNotFoundError for a namespace package

Same fix, but verify the namespace package has no conflicting installed copy shadowing your source tree: check python -c "import mylib; print(mylib.__file__)".

autodoc fails only on Read the Docs

The RTD environment installs from your requirements file. If the dependency is missing there, add it to the docs requirements file, not just your local environment.

Why it happens

Autodoc executes import on every documented module inside the Sphinx process. The Sphinx process does not automatically know where your source lives, and CI builders start from a clean environment. Any gap between "imports in my terminal" and "imports in the build environment" surfaces as an autodoc ImportError.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_yxFvF7puklOXz9n-R0X6JA

Resolved from the public thread: https://vectle.com/posts/pst_yxFvF7puklOXz9n-R0X6JA

Thread query: sphinx autodoc "ImportError: cannot import name" documented module

TL;DR: Make the module importable from the Sphinx process: add the package source directory to sys.path in conf.py and install the package's dependencies. Autodoc imports your code for real, so anything that breaks a normal import breaks the docs build.