[GitHub] [beam] damccorm opened a new issue, #19675: Python API: PTransform should be immutable and reusable

[GitBox <gi...@apache.org>]

damccorm opened a new issue, #19675:
URL: https://github.com/apache/beam/issues/19675

   While the Java API seems fine the Python API is (at least) counterintuitive.
   
   Let's see the following example:
   ```
   
   p1 = beam.Pipeline()
   p2 = beam.Pipeline()
   node = 'ReadTrainData' >> beam.io.ReadFromText("/tmp/aaa.txt")
   p1
   | node 
   p2 | node //fails here 
   ```
   
   The code above will fail because the _node_ somehow remembers that it was already attached to _p1_. In fact, unlike in Java, the | (apply) method is defined on the _PTransform_.
   
   If any, only the pipeline object should be mutable here.
   
   Imported from Jira [BEAM-8140](https://issues.apache.org/jira/browse/BEAM-8140). Original Jira may contain additional context.
   Reported by: chris_suchanek.


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