chadrik commented on a change in pull request #10822: [BEAM-7746] Minor typing
updates / fixes
URL: https://github.com/apache/beam/pull/10822#discussion_r384689098
##########
File path: sdks/python/apache_beam/transforms/external_java.py
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@@ -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 completely agree. Unfortunately, this is a syntax error in mypy:
```python
try:
from apache_beam.runners.dataflow.internal import apiclient # type:
Optional[types.ModuleType]
except ImportError:
apiclient = None
```
As is this:
```python
try:
import apache_beam.runners.dataflow.internal.apiclient as apiclient #
type: Optional[types.ModuleType]
except ImportError:
apiclient = None
```
The reason is that type comments are (by design) not capable of doing
anything that the new PEP 526 variable annotations are not. In other words,
this is obviously wrong:
```python
try:
Optional[types.ModuleType]: import
apache_beam.runners.dataflow.internal.apiclient as apiclient
except ImportError:
apiclient = None
```
In that context, this makes more sense:
```python
apiclient: Optional[types.ModuleType] = None
try:
from apache_beam.runners.dataflow.internal import apiclient
except ImportError:
pass
```
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