single-sourcing package version for setup.cfg Python projects

There are a couple of ways to do this (see below for the project structure used in these examples):

1.

setup.cfg

[metadata]
version = 1.2.3.dev4

src/my_top_level_package/__init__.py

import importlib.metadata
__version__ = importlib.metadata.version('MyProject')

2.

setup.cfg

[metadata]
version = file: VERSION.txt

VERSION.txt

1.2.3.dev4

src/my_top_level_package/__init__.py

import importlib.metadata
__version__ = importlib.metadata.version('MyProject')

3.

setup.cfg

[metadata]
version = attr: my_top_level_package.__version__

src/my_top_level_package/__init__.py

__version__ = '1.2.3.dev4'

And more...

There are probably other ways to do this, by playing with different combinatons.

References:

• https://setuptools.readthedocs.io/en/latest/userguide/declarative_config.html
• https://docs.python.org/3/library/importlib.metadata.html

Structure assumed in the previous examples is as follows...

MyProject
├── setup.cfg
├── setup.py
└── src
    └── my_top_level_package
        └── __init__.py

setup.py

#!/usr/bin/env python3

import setuptools

if __name__ == '__main__':
    setuptools.setup(
        # see 'setup.cfg'
    )

setup.cfg

[metadata]
name = MyProject
# See above for the value of 'version = ...'

[options]
package_dir =
    = src
packages = find:

[options.packages.find]
where = src

$ cd path/to/MyProject
$ python3 setup.py --version
1.2.3.dev4
$ python3 -m pip install .
# ...
$ python3 -c 'import my_top_level_package; print(my_top_level_package.__version__)'
1.2.3.dev4
$ python3 -V
Python 3.6.9
$ python3 -m pip list
Package       Version   
------------- ----------
MyProject     1.2.3.dev4
pip           20.0.2    
pkg-resources 0.0.0     
setuptools    45.2.0    
wheel         0.34.2    
zipp          3.0.0