Increase Python minimum version to 3.8

Once Ubuntu 20.04 has been out for a year and Anaconda supports it, let's update to Python 3.8.

changed due date to April 01, 2021

We will change it as soon as our computers are ubuntu 20.04, which should happen in the first quartal of 2021.

assigned to @holzer and unassigned @hoenig

Sounds good to me

mentioned in merge request !191 (merged)

My computer already has ubuntu 20.04 :D. And developers have their own environment anyway. I would upgrade.

We don't have to do it strictly by date, the issue deadline was meant as the earliest possible date. Is there any specific Python 3.8 feature you would like to use or some particularly ugly piece of code that could be cleaned up with Python 3.8 syntax? Until that is the case, upgrading is probably not worth the hassle.

Yes, I would agree with that. As far as I know, we don't actually use a python 3.8 feature so far so there is no real reason why not to support python 3.6 at the moment.

removed due date

unassigned @holzer

Alright, now even Debian stable has 3.9 as the default. And yes, there are some features, which I would like to use. The walrus operator, positional-only parameters for the API functions, more f-string features, and dataclasses. Plus, Python 3.10 will have structural pattern matching, which would help pystencils a lot. If we never update the requirement, we will never get there.

I would propose to have 3.8 as the minimal version, since the current LTS of Ubuntu has that.

I would be ok with that if there are features which really help pystencils. From my perspective it is not a good idea to just increase the restrictions for the sake of increasing them, or in other words as long as every piece of pystencils supports python 3.6 we should also have python 3.6 as minimal version. If you propose some code in pystencils which needs python 3.9 etc. and using python 3.9 makes the code indeed way better than I would say we can increase the minimal version immediately.

In the CI we already have a pipeline for python 3.9 so it pystencils should be completely compatible.

@kuron what is your opinion on that.

assigned to @hoenig

!259 (merged)

mentioned in merge request !259 (merged)

I would be ok with that if there are features which really help pystencils. [...] as long as every piece of pystencils supports python 3.6 we should also have python 3.6 as minimal version

I fully agree with you, @holzer. @hoenig, please add something to pystencils that requires Python 3.8. Right now the build on !259 (merged) passes even though we still have Docker images that contain Python 3.6 or 3.7.

We will add dataclasses for the creation functions in pystencils and lbmpy. This should make our top level functions better usable.

dataclasses

That‘s a 3.7 feature. Please find a 3.8 feature that is useful for pystencils and make use of it as part of !259 (merged).

assignment expression, positional-only parameters for the API functions, more f-string features

Moreover, today I started working on !261 (merged) and now it raises the question, whether we want to upgrade to 3.8 or 3.9. 3.9 introduced Type Hinting Generics In Standard Collections which I am (currently) using. I could implement it using the typing module (see List). But this would just increase the workload, since if we upgrade to any Python version >3.8 things like List is already deprecated.

I think pystencils desperetly needs type hints. And I also think that building for the past doesn't make any sense in a research environment. Should we then update directly to 3.9?

Wow, we can't go to 3.9 easily, because of conda. We tried it: https://i10git.cs.fau.de/pycodegen/pycodegen/-/jobs/625908