Python "importlib.metadata.PackageNotFoundError" in CI

Code asked importlib.metadata for a package’s version or metadata and none was found in the active environment. The distribution’s *.dist-info is not installed where this interpreter looks - usually a missing install or a wrong environment.

What this error means

A program crashes at startup with importlib.metadata.PackageNotFoundError: No package metadata was found for X, often from a version("X") call used to set __version__. The import of the module itself may succeed; only the metadata lookup fails.

Python traceback

importlib.metadata.PackageNotFoundError: No package metadata was found
for my-app
  File ".../__init__.py", line 3, in <module>
    __version__ = version("my-app")

Common causes

The distribution is not installed

Running from a source checkout without pip install means the code is importable but has no installed dist-info, so metadata lookups fail.

Name mismatch or wrong environment

The string passed to version() is the import name, not the distribution name (e.g. version("PIL") vs Pillow), or the script runs under a different venv than where the package was installed.

How to fix it

Install the project so its metadata exists

An editable install registers the dist-info so importlib.metadata can find it even when running from source.

Terminal

pip install -e .
python -c "from importlib.metadata import version; print(version('my-app'))"

Use the distribution name and guard the lookup

Pass the real distribution name, and fall back gracefully when running uninstalled.

Python

from importlib.metadata import version, PackageNotFoundError
try:
    __version__ = version("my-app")   # distribution name, not import name
except PackageNotFoundError:
    __version__ = "0.0.0+unknown"

How to prevent it

Install the project (editable is fine) before running code that reads its own metadata.
Pass the distribution name, not the import name, to version().
Guard metadata lookups so an uninstalled checkout degrades gracefully.