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https://issues.apache.org/jira/browse/SPARK-31525?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17094028#comment-17094028
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Holden Karau commented on SPARK-31525:
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I agree it's inconsistent, also the docs are a little misleading. I think the
root cause is we're using head as both `peek` and `take` which is why we've got
mixed metaphores. cc [~davies] who worked on this code most recently (2015) for
his thoughts.
> Inconsistent result of df.head(1) and df.head()
> -----------------------------------------------
>
> Key: SPARK-31525
> URL: https://issues.apache.org/jira/browse/SPARK-31525
> Project: Spark
> Issue Type: Bug
> Components: PySpark, SQL
> Affects Versions: 2.4.6, 3.0.0
> Reporter: Joshua Hendinata
> Priority: Minor
> Original Estimate: 24h
> Remaining Estimate: 24h
>
> In this line
> [https://github.com/apache/spark/blob/master/python/pyspark/sql/dataframe.py#L1339],
> if you are calling `df.head()` and dataframe is empty, it will return *None*
> but if you are calling `df.head(1)` and dataframe is empty, it will return
> *empty list* instead.
> This particular behaviour is not consistent and can create confusion.
> Especially when you are calling `len(df.head())` which will throw an
> exception for empty dataframe
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