Bump minimum python version to 3.9

[skushnir123]

Drops support for Python 3.7. and 3.8 For context, see issue: #6159

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[tanujkhattar]

We should drop support for both 3.7 and 3.8 and bump up the minimum version to 3.9. Fixing #6018 would further add support for 3.11

[tanujkhattar]

Main comment is to also drop support for Python 3.8. You'll also need to update asv.conf.json to Python 3.9.

[tanujkhattar]

Update to 3.9, here and elsewhere

[skushnir123]

Added 3.9 everywhere, as well as dropping some of the conditional checks for 3.7

[skushnir123]

Maybe we should make a follow-up ticket/issue to thoroughly search the code to ensure the cleanup form 3.7 and 3.8 is complete.

[tanujkhattar]

Should we also add py310 here?

[pavoljuhas]

Should we also add py310 here?

Yes, and py311 as well.

[skushnir123]

Added both of these, and updated the black formatter because the old version didn't support 311

[pavoljuhas]

Please also check all instances of sys.version and sys.version_info in the code and adjust as needed.
For example, it should be possible to remove the use_async_mock decorator because it only applies to 3.7

Cirq/cirq-google/cirq_google/engine/test_utils.py

Lines 22 to 24 in 6565fc5

	uses_async_mock = pytest.mark.xfail(
	sys.version_info < (3, 8, 0), reason='unittest.mock.AsyncMock is only available in python 3.8+'
	)

Another thing to check are all python_version specifiers in the requirement *.txt files.
For example, the dependency below can be removed if we require Python >= 3.9.

Cirq/cirq-core/requirements.txt

Lines 3 to 4 in 6565fc5

	# functools.cached_property was introduced in python 3.8
	backports.cached_property~=1.0.1; python_version < '3.8'

[skushnir123]

Main comment is to also drop support for Python 3.8. You'll also need to update asv.conf.json to Python 3.9.

Yup, made these changes

[pavoljuhas]

Almost there, however there are few more things relevant only for abandoned Pythons. Please consider updating your PR with

git pull https://github.com/pavoljuhas/Cirq.git pr6167-amend-1

skushnir123/Cirq@drop-37...pavoljuhas:pr6167-amend-1

There are also Dockerfile-s that use old python and will need update, but that is perhaps better left for another PR - unless they block the tests here, #6175.

[skushnir123]

git pull https://github.com/pavoljuhas/Cirq.git pr6167-amend-1

Thanks for adding on those changes! I just added those to my PR. Let me know if there is anything else to remove/change.

[skushnir123]

Almost there, however there are few more things relevant only for abandoned Pythons. Please consider updating your PR with

git pull https://github.com/pavoljuhas/Cirq.git pr6167-amend-1

skushnir123/Cirq@drop-37...pavoljuhas:pr6167-amend-1

There are also Dockerfile-s that use old python and will need update, but that is perhaps better left for another PR - unless they block the tests here, #6175.

I don't think the Dockerfile's are failing any tests here.

[pavoljuhas]

Thanks for taking care of this!

[tanujkhattar]

Thanks Samuel and Pavol! I've removed Python 3.7 and 3.8 from required CI checks and the PR is ready to be merged now!