sdks/python/apache_beam/examples/streaming_wordcap.py

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"""A streaming string-capitalization workflow.

Important: streaming pipeline support in Python Dataflow is in development
and is not yet available for use.
"""

from __future__ import absolute_import

import argparse
import logging

import apache_beam as beam


def run(argv=None):
  """Build and run the pipeline."""

  parser = argparse.ArgumentParser()
  parser.add_argument(
      '--input_topic', dest='input_topic', required=True,
      help='Input PubSub topic of the form "/topics/<PROJECT>/<TOPIC>".')
  parser.add_argument(
      '--output_topic', dest='output_topic', required=True,
      help='Output PubSub topic of the form "/topics/<PROJECT>/<TOPIC>".')
  known_args, pipeline_args = parser.parse_known_args(argv)

  with beam.Pipeline(argv=pipeline_args) as p:

    # Read the text file[pattern] into a PCollection.
    lines = p | beam.io.ReadStringsFromPubSub(known_args.input_topic)

    # Capitalize the characters in each line.
    transformed = (lines
                   | 'capitalize' >> (beam.Map(lambda x: x.upper())))

    # Write to PubSub.
    # pylint: disable=expression-not-assigned
    transformed | beam.io.WriteStringsToPubSub(known_args.output_topic)


if __name__ == '__main__':
  logging.getLogger().setLevel(logging.INFO)
  run()