chadrik commented on a change in pull request #10822: [BEAM-7746] Minor typing updates / fixes URL: https://github.com/apache/beam/pull/10822#discussion_r384836306
########## File path: sdks/python/apache_beam/transforms/external_java.py ########## @@ -37,18 +39,19 @@ # Protect against environments where apitools library is not available. # pylint: disable=wrong-import-order, wrong-import-position +apiclient = None # type: Optional[types.ModuleType] Review comment: I did some more research on this, and I found this mypy issue: https://github.com/python/mypy/issues/1297 It suggests this idiom: ```python try: from apache_beam.runners.dataflow.internal import apiclient as _apiclient except ImportError: apiclient = None else: apiclient = _apiclient ``` The import is a bit longer and uglier, but it has 2 advantages: - no need to import `Optional` or `ModuleType` - the idiom I was using was actually making `apiclient` a generic ModuleType, dropping all knowledge of the members of `apache_beam.runners.dataflow.internal`. That's bad! The reason this works without explicit `Optional` annotation that mypy will automatically determine optionality in some cases, like this: ```python if some_conditional(): x = None else: x = 1 reveal_type(x) # Revealed type is 'Union[builtins.int, None]' ``` ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
