Add minimum required Python version

[Rotzbua]

Change

• Add minimum required Python version
• Add test for every alive Python version (except broken 3.12)

[coveralls]

coverage: 88.889% (+1.0%) from 87.847% when pulling d7b3918 on Rotzbua:add_python_requirement into 5e9ef5d on JohannesBuchner:master.

[JohannesBuchner]

what causes this change? for both.

[JohannesBuchner]

What is the oldest python version we can support? I think it is driven by the requirements, not this package.

[Rotzbua]

The oldest version is python 3.8. Everything else is EOL:
https://devguide.python.org/versions/

[Rotzbua]

what causes this change? for both.

pip supports proper dependency resolution. For this it needs the supported Python versions.
Good programming paradigm: only claim to support something when it is tested.

[JohannesBuchner]

I am closing this because it is not properly justified.

Firstly, just because the Python project does not provide support for older versions, does not mean imagehash is incompatible.

Second, passing tests is a requirement for compatible versions, but there may be compatible versions beyond the tests currently set up. We also do not test all patch versions of python, yet assume they are compatible.

Imagehash is pure python code. The compatibility is introduced by dependencies. We do not need to document these dependencies here, because pip will look them up as needed.

There is a cost associated to testing "all" or a large number of python versions, namely a carbon footprint on the computing center for every git push. It seems to me we do not gain substantial information here by testing intermediate versions over testing the earliest and latest supported python version.

[Rotzbua]

Firstly, just because the Python project does not provide support for older versions, does not mean imagehash is incompatible.

The statement contradicts itself, because the project does not make any statement about the actively supported Python versions.
The python_requires attribute can be overridden by a command to pip. But then the programmer is actively aware that the library version may not be compatible.
Not specifying a minimum version also limits further development, since new Python language features cannot be used. For example, it is totally normal to use features like typing or f-strings for coding.

Imagehash is pure python code. The compatibility is introduced by dependencies.

This is simply wrong. Python code is processed by the Python interpreter and thus has a clear dependency on it.
Furthermore, "pure" is to be understood only in the sense of written in a single programming language. There is no universally (pure) valid python code, because the programming language is also constantly evolving.

There is a cost associated to testing "all" or a large number of python versions, namely a carbon footprint on the computing center for every git push.

• The trigger points for test runs can be customized.
• CI CPU time consumption can be reduced by caching.
• For those reason the number of supported python versions is limited.
• In my opinion distributing buggy code causes more CO2 than testing it at one point in the chain.