Python 3.8 compatibility

[Blebowski]

Hi,

I am trying to bring-up the PDK on RHEL 8 system. Unfortunately, the latest Python I have, is 3.8
(and this is still higher than the default which is 3.6).

We are planning to get later version of Python installed, but ATM this is the best I can do.

I built Klayout v0.30.0 with Python interpreter 3.8 and also matching libraries. When I try
to use Klayout with KLAYOUT_PATH and KLAYOUT_HOME as in your manual, the Klayout
PDK scripting throws errors (and PCells do not work). I digged into these and there were only
two types of issues only on couple of places:

1. usage of list needed to be replaced by typing.List (using from futures import annotations adviced by stack overflow did not work, no idea why).
2. The match statement added in Python 3.10 needed to be rewritten to if-elif-elif in couple of places.

With these changes, I got the Klayout PCells working with Python 3.8.

I understand that the PDK is primarily developed on Ubuntu 22.04, which has sth like 3.11.
However, I am wondering if it would not be worth to avoid few of the syntactic sugar stuff
to be slightly backwards compatible with older systems.

I am wondering if it would be even possible to get it working with Python 3.6. 3.8 is the default
on RHEL8. Many companies using commercial toolchains are "stuck" with RHEL 8 on their machines
since, e.g. Synopsys tools need RHEL8 for now. Even RHEL9 has default Python version of 3.9
which does not yet include the match statement. Also, Synopsys for commercial EDA tools does
not even support the RHEL 9 yet:
https://www.synopsys.com/support/licensing-installation-computeplatforms/compute-platforms/compute-platforms-roadmap.html

I am thinking it may increase IHP130 adoption if the tools are easier to bring-up in typical
"commercial ASIC development department machines".

[sergeiandreyev]

Hi @Blebowski, thank you for starting this! This is actually a part of ongoing internal discussion..
fyi, @ThomasZecha, @KrzysztofHerman

[Blebowski]

Great, I can provide a PR to do the changes. Should I do so ?

[ThomasZecha]

Yes, please!

[Blebowski]

Hi,

@ThomasZecha, I have rebased to your changes in Klayout PCells API from today, and
all seems to work:
IHP-GmbH/pycell4klayout-api#2