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https://issues.apache.org/jira/browse/BEAM-7060?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16847176#comment-16847176
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Chad Dombrova commented on BEAM-7060:
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> By supporting I mean adding adding annotations to Beam (note that Beam still
> support Python 2 so inline annotations aren't possible yet).
So I assume that means you would use type comments? Where I work we are also
stuck supporting python2, so we use a tool to generate type comments from
docstrings: [https://pypi.org/project/doc484/].
> Beam uses type hints to determine which coders to use for pipeline elements.
yes, this will be ugly to support using pep484 type comments, though it is
possible. (you can parse the type name from type comments and then attempt to
get a reference to the type object. as noted in the google doc, this is what
pytypes does)
> Beam constructs pipelines using the pipe symbol/apply() method. The operands
>are classes (PTransforms), which don't get type hints in Python (AFAIK).
It may be possible to make PTransforms a Generic class which is parameterized
by its input/output types.
Anyway, it's really exciting to see the thought being put into this task. It
definitely sounds like it's headed in the right direction.
> Design Py3-compatible typehints annotation support in Beam 3.
> -------------------------------------------------------------
>
> Key: BEAM-7060
> URL: https://issues.apache.org/jira/browse/BEAM-7060
> Project: Beam
> Issue Type: Sub-task
> Components: sdk-py-core
> Reporter: Valentyn Tymofieiev
> Assignee: Udi Meiri
> Priority: Major
>
> Existing [Typehints implementaiton in
> Beam|[https://github.com/apache/beam/blob/master/sdks/python/apache_beam/typehints/
> ] heavily relies on internal details of CPython implementation, and some of
> the assumptions of this implementation broke as of Python 3.6, see for
> example: https://issues.apache.org/jira/browse/BEAM-6877, which makes
> typehints support unusable on Python 3.6 as of now. [Python 3 Kanban
> Board|https://issues.apache.org/jira/secure/RapidBoard.jspa?rapidView=245&view=detail]
> lists several specific typehints-related breakages, prefixed with "TypeHints
> Py3 Error".
> We need to decide whether to:
> - Deprecate in-house typehints implementation.
> - Continue to support in-house implementation, which at this point is a stale
> code and has other known issues.
> - Attempt to use some off-the-shelf libraries for supporting
> type-annotations, like Pytype, Mypy, PyAnnotate.
> WRT to this decision we also need to plan on immediate next steps to unblock
> adoption of Beam for Python 3.6+ users. One potential option may be to have
> Beam SDK ignore any typehint annotations on Py 3.6+.
> cc: [~udim], [~altay], [~robertwb].
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