GroupByKey

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Takes a keyed collection of elements and produces a collection where each element consists of a key and all values associated with that key.

See more information in the Beam Programming Guide.

Examples

In the following example, we create a pipeline with a PCollection of produce keyed by season.

We use GroupByKey to group all the produce for each season.

import apache_beam as beam

with beam.Pipeline() as pipeline:
  produce_counts = (
      pipeline
      | 'Create produce counts' >> beam.Create([
          ('spring', '🍓'),
          ('spring', '🥕'),
          ('spring', '🍆'),
          ('spring', '🍅'),
          ('summer', '🥕'),
          ('summer', '🍅'),
          ('summer', '🌽'),
          ('fall', '🥕'),
          ('fall', '🍅'),
          ('winter', '🍆'),
      ])
      | 'Group counts per produce' >> beam.GroupByKey()
      | beam.MapTuple(lambda k, vs: (k, sorted(vs)))  # sort and format
      | beam.Map(print))

Output:

('spring', ['🍓', '🥕', '🍆', '🍅'])
('summer', ['🥕', '🍅', '🌽'])
('fall', ['🥕', '🍅'])
('winter', ['🍆'])
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