[SPARK-47132][DOCS][PYTHON] Correct docstring for pyspark's dataframe.head #45197
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The docstring claimed that `head(n)` would return a `Row` (rather than a list of rows) iff n == 1, but that's incorrect. Type hints, example, and implementation show that the difference between row or list of rows lies in whether n is supplied at all -- if it isn't, `head()` returns a `Row`, if it is, even if it is 1, `head(n)` returns a list. This commit corrects the docstring.
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Good catch! Thanks for working on that! Would you create a JIRA and add the JIRA number to the PR title, along with Also feel free to answer no to |
python/pyspark/sql/dataframe.py
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| @@ -3526,8 +3526,8 @@ def head(self, n: Optional[int] = None) -> Union[Optional[Row], List[Row]]: | |||
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| Returns | |||
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| If n is greater than 1, return a list of :class:`Row`. | |||
| If n is 1, return a single Row. | |||
| If n is supplied, return a list of :class:`Row`. | |||
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>>> spark.range(3).head(0)
[]I'm wondering if we should call out the empty list when n=0.
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Good point. I'm suggesting adding this as an example, and extending the returns section to mention the length of the list (see commit below).
wunderalbert
changed the title
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Thank you @xinrong-meng ! I've created the JIRA and edited the PR. |
| @@ -3526,8 +3526,9 @@ def head(self, n: Optional[int] = None) -> Union[Optional[Row], List[Row]]: | |||
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| Returns | |||
| ------- | |||
| If n is greater than 1, return a list of :class:`Row`. | |||
| If n is 1, return a single Row. | |||
| If n is supplied, return a list of :class:`Row` of length n | |||
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The description is so much better! Thanks!
xinrong-meng
approved these changes
Feb 22, 2024
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Merged to master, thank you! |
ericm-db
pushed a commit
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Mar 5, 2024
….head ### What changes were proposed in this pull request? Change description of `returns` in docstring for pyspark's dataframe's `head` to match actual behaviour. ### Why are the changes needed? The docstring claimed that `head(n)` would return a `Row` (rather than a list of rows) iff n == 1, but that's incorrect. Type hints, example, and implementation show that the difference between row or list of rows lies in whether n is supplied at all -- if it isn't, `head()` returns a `Row`, if it is, even if it is 1, `head(n)` returns a list. ### Does this PR introduce _any_ user-facing change? No, only a Python docstring is changed. ### How was this patch tested? No tests were added since only docs changed. ### Was this patch authored or co-authored using generative AI tooling? No. Closes apache#45197 from wunderalbert/patch-1. Authored-by: Albert Ziegler <55346556+wunderalbert@users.noreply.github.com> Signed-off-by: Xinrong Meng <xinrong@apache.org>
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What changes were proposed in this pull request?
Change description of
returnsin docstring for pyspark's dataframe'sheadto match actual behaviour.Why are the changes needed?
The docstring claimed that
head(n)would return aRow(rather than a list of rows) iff n == 1, but that's incorrect.Type hints, example, and implementation show that the difference between row or list of rows lies in whether n is supplied at all -- if it isn't,
head()returns aRow, if it is, even if it is 1,head(n)returns a list.Does this PR introduce any user-facing change?
No, only a Python docstring is changed.
How was this patch tested?
No tests were added since only docs changed.
Was this patch authored or co-authored using generative AI tooling?
No.