Github user HyukjinKwon commented on a diff in the pull request:
https://github.com/apache/spark/pull/18732#discussion_r142029696
--- Diff: python/pyspark/sql/functions.py ---
@@ -2181,31 +2186,69 @@ def udf(f=None, returnType=StringType()):
@since(2.3)
def pandas_udf(f=None, returnType=StringType()):
"""
- Creates a :class:`Column` expression representing a user defined
function (UDF) that accepts
- `Pandas.Series` as input arguments and outputs a `Pandas.Series` of
the same length.
+ Creates a :class:`Column` expression representing a vectorized user
defined function (UDF).
+
+ The user-defined function can define one of the following
transformations:
+ 1. One or more `pandas.Series` -> A `pandas.Series`
+
+ This udf is used with `DataFrame.withColumn` and `DataFrame.select`.
+ The returnType should be a primitive data type, e.g., DoubleType()
+
+ Example:
+
+ >>> from pyspark.sql.types import IntegerType, StringType
+ >>> slen = pandas_udf(lambda s: s.str.len(), IntegerType())
+ >>> @pandas_udf(returnType=StringType())
+ ... def to_upper(s):
+ ... return s.str.upper()
+ ...
+ >>> @pandas_udf(returnType="integer")
+ ... def add_one(x):
+ ... return x + 1
+ ...
+ >>> df = spark.createDataFrame([(1, "John Doe", 21)], ("id",
"name", "age"))
+ >>> df.select(slen("name").alias("slen(name)"), to_upper("name"),
add_one("age")) \\
+ ... .show() # doctest: +SKIP
+ +----------+--------------+------------+
+ |slen(name)|to_upper(name)|add_one(age)|
+ +----------+--------------+------------+
+ | 8| JOHN DOE| 22|
+ +----------+--------------+------------+
+
+ 2. A `pandas.DataFrame` -> A `pandas.DataFrame`
--- End diff --
This looks producing an warning here:
```
spark/python/pyspark/sql/functions.py:docstring of
pyspark.sql.functions.pandas_udf:46: WARNING: Enumerated list ends without a
blank line; unexpected unindent.
```
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