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https://issues.apache.org/jira/browse/BEAM-9547?focusedWorklogId=604843&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-604843
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ASF GitHub Bot logged work on BEAM-9547:
----------------------------------------
Author: ASF GitHub Bot
Created on: 02/Jun/21 00:40
Start Date: 02/Jun/21 00:40
Worklog Time Spent: 10m
Work Description: TheNeuralBit commented on a change in pull request
#14922:
URL: https://github.com/apache/beam/pull/14922#discussion_r643573673
##########
File path: sdks/python/apache_beam/dataframe/frames.py
##########
@@ -458,6 +458,32 @@ def size(self):
requires_partition_by=partitionings.Singleton(),
preserves_partition_by=partitionings.Singleton()))
+ def length(self):
+ """Alternative to ``len(df)`` which returns a deferred result that can be
+ used in arithmetic with :class:`DeferredSeries` or
+ :class:`DeferredDataFrame` instances."""
+ lengths = expressions.ComputedExpression(
+ 'get_lengths',
+ # Wrap scalar results in a Series for easier concatenation later
+ lambda df: pd.Series(len(df)),
+ [self._expr],
+ requires_partition_by=partitionings.Arbitrary(),
+ preserves_partition_by=partitionings.Singleton())
+
+ with expressions.allow_non_parallel_operations(True):
+ return frame_base.DeferredFrame.wrap(
+ expressions.ComputedExpression(
+ 'sum_lengths',
+ lambda lengths: lengths.sum(), [lengths],
+ requires_partition_by=partitionings.Singleton(),
+ preserves_partition_by=partitionings.Singleton()))
+
+ def __len__(self):
+ raise frame_base.WontImplementError(
+ "len(df) is not currently supported because it produces a non-deferred
"
+ "result. Consider using df.length() instead.",
+ reason="non-deferred-result")
Review comment:
yeah I felt the same way! Unfortunately I tried this and found that
Python requires `__len__` to return an integer and raises if it's not
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Issue Time Tracking
-------------------
Worklog Id: (was: 604843)
Time Spent: 97h 40m (was: 97.5h)
> Implement all pandas operations (or raise WontImplementError)
> -------------------------------------------------------------
>
> Key: BEAM-9547
> URL: https://issues.apache.org/jira/browse/BEAM-9547
> Project: Beam
> Issue Type: Improvement
> Components: sdk-py-core
> Reporter: Brian Hulette
> Assignee: Robert Bradshaw
> Priority: P2
> Labels: dataframe-api
> Time Spent: 97h 40m
> Remaining Estimate: 0h
>
> We should have an implementation for every DataFrame, Series, and GroupBy
> method. Everything that's not possible to implement should get a default
> implementation that raises WontImplementError
> See https://github.com/apache/beam/pull/10757#discussion_r389132292
> Progress at the individual operation level is tracked in a
> [spreadsheet|https://docs.google.com/spreadsheets/d/1hHAaJ0n0k2tw465ORs5tfdy4Lg0DnGWIQ53cLjAhel0/edit],
> consider requesting edit access if you'd like to help out.
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