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.. _access-packaging-metadata:
=================================================
Accessing Briefcase packaging metadata at runtime
=================================================
When Briefcase installs your app, it adds a `PEP566
<https://peps.python.org/pep-0566/>`__ metadata file containing information
about your app, and Briefcase itself. You can retrieve this information at
runtime using the `Python builtin library 'importlib.metadata'
<https://docs.python.org/3/library/importlib.metadata.html>`__.
``importlib.metadata`` was added in Python 3.8; however, it has been backported
and published on PyPI as `'importlib_metadata'
<https://pypi.org/project/importlib-metadata/>`__ for older versions of Python.
To access application metadata at runtime, you can use the following code::
import sys
try:
from importlib import metadata as importlib_metadata
except ImportError:
# Backwards compatibility - importlib.metadata was added in Python 3.8
import importlib_metadata
# Find the name of the module that was used to start the app
app_module = sys.modules['__main__'].__package__
# Retrieve the app's metadata
metadata = importlib_metadata.metadata(app_module)
The ``metadata`` returned by this code will be a dictionary-like object that
contains the following identifying keys:
* **Metadata-Version** - The syntax version of the metadata file itself (as
defined in `PEP566 <https://peps.python.org/pep-0566/>`__).
* **Briefcase-Version** - The version of Briefcase used to package the app.
The existence of this key in app metadata can be used to identify if your
application code is running in a Briefcase container; it will only exist if
the app has been packaged by Briefcase.
It will also have the following keys, derived from your application's
``pyproject.toml`` configuration:
* **Name** - ``app_name``
* **Formal-Name** - ``formal_name``
* **App-ID** - ``bundle`` and ``app_name``, joined with a ``.``
* **Version** - ``version``
* **Summary** - ``description``
The metadata may also contain the following keys, if they have been defined
in your app's ``pyproject.toml`` configuration:
* **Home-page** - ``url``
* **Author** - ``author``
* **Author-email** - ``author_email``
For example, the metadata for the app constructed by the `BeeWare Tutorial
<https://docs.beeware.org/en/latest/tutorial/tutorial-1.html>`_ would
contain::
Metadata-Version: 2.1
Briefcase-Version: 0.3.1
Name: helloworld
Formal-Name: Hello World
App-ID: com.example.helloworld
Version: 0.0.1
Home-page: https://example.com/helloworld
Author: Jane Developer
Author-email: jane@example.com
Summary: My first application
|
