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new 85a35954 Add docstring examples for Aggregate window functions (#1418)
85a35954 is described below
commit 85a3595444e7946dc4eaa166cb4843bee2bf2f07
Author: Nick <[email protected]>
AuthorDate: Wed Mar 18 22:06:31 2026 -0400
Add docstring examples for Aggregate window functions (#1418)
* Add docstring examples for Aggregate window functions
Add example usage to docstrings for Aggregate window functions to improve
documentation.
Co-Authored-By: Claude Opus 4.6 <[email protected]>
* Remove for example for example docstring
* Actually remove all for example calls in favor of docstrings
* Remove builtins
* Make google docstyle
* Fix bad merge leading to duplicate xample
---------
Co-authored-by: Claude Opus 4.6 <[email protected]>
---
python/datafusion/functions.py | 127 ++++++++++++++++++++++++++++-------------
1 file changed, 87 insertions(+), 40 deletions(-)
diff --git a/python/datafusion/functions.py b/python/datafusion/functions.py
index a4933a74..e85d710e 100644
--- a/python/datafusion/functions.py
+++ b/python/datafusion/functions.py
@@ -3323,10 +3323,6 @@ def array_agg(
filter: If provided, only compute against rows for which the filter is
True
order_by: Order the resultant array values. Accepts column names or
expressions.
- For example::
-
- df.aggregate([], array_agg(col("a"), order_by="b"))
-
Examples:
---------
>>> ctx = dfn.SessionContext()
@@ -4047,9 +4043,14 @@ def first_value(
column names or expressions.
null_treatment: Assign whether to respect or ignore null values.
- For example::
-
- df.aggregate([], first_value(col("a"), order_by="ts"))
+ Examples:
+ >>> ctx = dfn.SessionContext()
+ >>> df = ctx.from_pydict({"a": [10, 20, 30]})
+ >>> result = df.aggregate(
+ ... [], [dfn.functions.first_value(dfn.col("a")).alias("v")]
+ ... )
+ >>> result.collect_column("v")[0].as_py()
+ 10
"""
order_by_raw = sort_list_to_raw_sort_list(order_by)
filter_raw = filter.expr if filter is not None else None
@@ -4084,9 +4085,14 @@ def last_value(
column names or expressions.
null_treatment: Assign whether to respect or ignore null values.
- For example::
-
- df.aggregate([], last_value(col("a"), order_by="ts"))
+ Examples:
+ >>> ctx = dfn.SessionContext()
+ >>> df = ctx.from_pydict({"a": [10, 20, 30]})
+ >>> result = df.aggregate(
+ ... [], [dfn.functions.last_value(dfn.col("a")).alias("v")]
+ ... )
+ >>> result.collect_column("v")[0].as_py()
+ 30
"""
order_by_raw = sort_list_to_raw_sort_list(order_by)
filter_raw = filter.expr if filter is not None else None
@@ -4123,9 +4129,14 @@ def nth_value(
column names or expressions.
null_treatment: Assign whether to respect or ignore null values.
- For example::
-
- df.aggregate([], nth_value(col("a"), 2, order_by="ts"))
+ Examples:
+ >>> ctx = dfn.SessionContext()
+ >>> df = ctx.from_pydict({"a": [10, 20, 30]})
+ >>> result = df.aggregate(
+ ... [], [dfn.functions.nth_value(dfn.col("a"), 2).alias("v")]
+ ... )
+ >>> result.collect_column("v")[0].as_py()
+ 20
"""
order_by_raw = sort_list_to_raw_sort_list(order_by)
filter_raw = filter.expr if filter is not None else None
@@ -4303,9 +4314,14 @@ def lead(
order_by: Set ordering within the window frame. Accepts
column names or expressions.
- For example::
-
- lead(col("b"), order_by="ts")
+ Examples:
+ >>> ctx = dfn.SessionContext()
+ >>> df = ctx.from_pydict({"a": [1, 2, 3]})
+ >>> result = df.select(
+ ... dfn.col("a"), dfn.functions.lead(dfn.col("a"), shift_offset=1,
+ ... default_value=0, order_by="a").alias("lead"))
+ >>> result.sort(dfn.col("a")).collect_column("lead").to_pylist()
+ [2, 3, 0]
"""
if not isinstance(default_value, pa.Scalar) and default_value is not None:
default_value = pa.scalar(default_value)
@@ -4358,9 +4374,14 @@ def lag(
order_by: Set ordering within the window frame. Accepts
column names or expressions.
- For example::
-
- lag(col("b"), order_by="ts")
+ Examples:
+ >>> ctx = dfn.SessionContext()
+ >>> df = ctx.from_pydict({"a": [1, 2, 3]})
+ >>> result = df.select(
+ ... dfn.col("a"), dfn.functions.lag(dfn.col("a"), shift_offset=1,
+ ... default_value=0, order_by="a").alias("lag"))
+ >>> result.sort(dfn.col("a")).collect_column("lag").to_pylist()
+ [0, 1, 2]
"""
if not isinstance(default_value, pa.Scalar):
default_value = pa.scalar(default_value)
@@ -4403,9 +4424,13 @@ def row_number(
order_by: Set ordering within the window frame. Accepts
column names or expressions.
- For example::
-
- row_number(order_by="points")
+ Examples:
+ >>> ctx = dfn.SessionContext()
+ >>> df = ctx.from_pydict({"a": [10, 20, 30]})
+ >>> result = df.select(
+ ... dfn.col("a"),
dfn.functions.row_number(order_by="a").alias("rn"))
+ >>> result.sort(dfn.col("a")).collect_column("rn").to_pylist()
+ [1, 2, 3]
"""
partition_by_raw = expr_list_to_raw_expr_list(partition_by)
order_by_raw = sort_list_to_raw_sort_list(order_by)
@@ -4447,9 +4472,14 @@ def rank(
order_by: Set ordering within the window frame. Accepts
column names or expressions.
- For example::
-
- rank(order_by="points")
+ Examples:
+ >>> ctx = dfn.SessionContext()
+ >>> df = ctx.from_pydict({"a": [10, 10, 20]})
+ >>> result = df.select(
+ ... dfn.col("a"), dfn.functions.rank(order_by="a").alias("rnk")
+ ... )
+ >>> result.sort(dfn.col("a")).collect_column("rnk").to_pylist()
+ [1, 1, 3]
"""
partition_by_raw = expr_list_to_raw_expr_list(partition_by)
order_by_raw = sort_list_to_raw_sort_list(order_by)
@@ -4486,9 +4516,13 @@ def dense_rank(
order_by: Set ordering within the window frame. Accepts
column names or expressions.
- For example::
-
- dense_rank(order_by="points")
+ Examples:
+ >>> ctx = dfn.SessionContext()
+ >>> df = ctx.from_pydict({"a": [10, 10, 20]})
+ >>> result = df.select(
+ ... dfn.col("a"),
dfn.functions.dense_rank(order_by="a").alias("dr"))
+ >>> result.sort(dfn.col("a")).collect_column("dr").to_pylist()
+ [1, 1, 2]
"""
partition_by_raw = expr_list_to_raw_expr_list(partition_by)
order_by_raw = sort_list_to_raw_sort_list(order_by)
@@ -4526,9 +4560,14 @@ def percent_rank(
order_by: Set ordering within the window frame. Accepts
column names or expressions.
- For example::
- percent_rank(order_by="points")
+ Examples:
+ >>> ctx = dfn.SessionContext()
+ >>> df = ctx.from_pydict({"a": [10, 20, 30]})
+ >>> result = df.select(
+ ... dfn.col("a"),
dfn.functions.percent_rank(order_by="a").alias("pr"))
+ >>> result.sort(dfn.col("a")).collect_column("pr").to_pylist()
+ [0.0, 0.5, 1.0]
"""
partition_by_raw = expr_list_to_raw_expr_list(partition_by)
order_by_raw = sort_list_to_raw_sort_list(order_by)
@@ -4566,9 +4605,17 @@ def cume_dist(
order_by: Set ordering within the window frame. Accepts
column names or expressions.
- For example::
-
- cume_dist(order_by="points")
+ Examples:
+ >>> ctx = dfn.SessionContext()
+ >>> df = ctx.from_pydict({"a": [1., 2., 2., 3.]})
+ >>> result = df.select(
+ ... dfn.col("a"),
+ ... dfn.functions.cume_dist(
+ ... order_by="a"
+ ... ).alias("cd")
+ ... )
+ >>> result.collect_column("cd").to_pylist()
+ [0.25..., 0.75..., 0.75..., 1.0...]
"""
partition_by_raw = expr_list_to_raw_expr_list(partition_by)
order_by_raw = sort_list_to_raw_sort_list(order_by)
@@ -4610,9 +4657,13 @@ def ntile(
order_by: Set ordering within the window frame. Accepts
column names or expressions.
- For example::
-
- ntile(3, order_by="points")
+ Examples:
+ >>> ctx = dfn.SessionContext()
+ >>> df = ctx.from_pydict({"a": [10, 20, 30, 40]})
+ >>> result = df.select(
+ ... dfn.col("a"), dfn.functions.ntile(2, order_by="a").alias("nt"))
+ >>> result.sort(dfn.col("a")).collect_column("nt").to_pylist()
+ [1, 1, 2, 2]
"""
partition_by_raw = expr_list_to_raw_expr_list(partition_by)
order_by_raw = sort_list_to_raw_sort_list(order_by)
@@ -4648,10 +4699,6 @@ def string_agg(
order_by: Set the ordering of the expression to evaluate. Accepts
column names or expressions.
- For example::
-
- df.aggregate([], string_agg(col("a"), ",", order_by="b"))
-
Examples:
---------
>>> ctx = dfn.SessionContext()
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