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https://issues.apache.org/jira/browse/BEAM-7840?focusedWorklogId=284968&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-284968
]
ASF GitHub Bot logged work on BEAM-7840:
----------------------------------------
Author: ASF GitHub Bot
Created on: 30/Jul/19 14:05
Start Date: 30/Jul/19 14:05
Worklog Time Spent: 10m
Work Description: tvalentyn commented on pull request #9168: [BEAM-7840]
Provide MapTuple and FlatMapTuple for Python 3 users.
URL: https://github.com/apache/beam/pull/9168#discussion_r308707480
##########
File path: sdks/python/apache_beam/transforms/core.py
##########
@@ -1316,6 +1322,142 @@ def Map(fn, *args, **kwargs): # pylint:
disable=invalid-name
return pardo
+def MapTuple(fn, *args, **kwargs): # pylint: disable=invalid-name
+ r""":func:`MapTuple` is like :func:`Map` but expects tuple inputs and
+ flattens them into multiple input arguments.
+
+ beam.MapTuple(lambda a, b, ...: ...)
+
+ is equivalent to Python 2
+
+ beam.Map(lambda (a, b, ...), ...: ...)
+
+ In other words
+
+ beam.MapTuple(fn)
+
+ is equivalent to
+
+ beam.Map(lambda element, ...: fn(\*element, ...))
+
+ This can be useful when processing a PCollection of tuples
+ (e.g. key-value pairs).
+
+ Args:
+ fn (callable): a callable object.
+ *args: positional arguments passed to the transform callable.
+ **kwargs: keyword arguments passed to the transform callable.
+
+ Returns:
+ ~apache_beam.pvalue.PCollection:
+ A :class:`~apache_beam.pvalue.PCollection` containing the
+ :func:`MapTuple` outputs.
+
+ Raises:
+ ~exceptions.TypeError: If the **fn** passed as argument is not a callable.
+ Typical error is to pass a :class:`DoFn` instance which is supported only
+ for :class:`ParDo`.
+ """
+ if not callable(fn):
+ raise TypeError(
+ 'MapTuple can be used only with callable objects. '
+ 'Received %r instead.' % (fn))
+
+ if _fn_takes_side_inputs(fn):
Review comment:
implementation of `_fn_takes_side_inputs` relies on a fact that `fn` accepts
only one argument that is not a side-input. It seems that this assumption does
not hold for fn that expects an unfolded tuple (multiple arguments which are
not side-inputs). Should we just remove the `if` and always go through the
positive branch? There is the same branch in `FlatMapTuple`, and actually in
`Map`/`FlatMap` as well. I wonder if this could be simplified everywhere. WDYT?
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Issue Time Tracking
-------------------
Worklog Id: (was: 284968)
> Create MapTuple and FlatMapTuple to ease migration to Python 3.
> ---------------------------------------------------------------
>
> Key: BEAM-7840
> URL: https://issues.apache.org/jira/browse/BEAM-7840
> Project: Beam
> Issue Type: Test
> Components: sdk-py-core
> Reporter: Robert Bradshaw
> Priority: Major
> Time Spent: 20m
> Remaining Estimate: 0h
>
> These are like Map and FlatMap but expand out tuple input elements across
> several arguments. This will be useful as tuple argument unpacking has been
> removed in Python 3. Instead of having to convert
> Map(lambda (k, v): expresion(k, v))
> into
> Map(lambda k_v: expression(k_v[0], k_v[1]))
> one can now write
> MapTuple(lambda k, v: expression(k, v))
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