---
title: "Flatten"
---
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# Flatten
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<br><br>



Merges multiple `PCollection` objects into a single logical
`PCollection`. A transform for `PCollection` objects
that store the same data type. 

See more information in the [Beam Programming Guide](/documentation/programming-guide/#flatten).

## Examples
See [BEAM-7391](https://issues.apache.org/jira/browse/BEAM-7391) for updates. 

## Related transforms
* [FlatMap](/documentation/transforms/python/elementwise/flatmap) applies a simple 1-to-many mapping
  function over each element in the collection. This transform might produce zero
  or more outputs.