[GitHub] spark pull request #18732: [SPARK-20396][SQL][PySpark] groupby().apply() wit...

[HyukjinKwon]

Github user HyukjinKwon commented on a diff in the pull request:

    https://github.com/apache/spark/pull/18732#discussion_r142029714
  
    --- 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`
    +
    +       This udf is used with `GroupedData.apply`
    +       The returnType should be a StructType describing the schema of the 
returned
    +       `pandas.DataFrame`.
    +
    +       Example:
    +
    +       >>> df = spark.createDataFrame([(1, 1.0), (1, 2.0), (2, 3.0), (2, 
4.0)], ("id", "v"))
    +       >>> @pandas_udf(returnType=df.schema)
    +       ... def normalize(df):
    +       ...     v = df.v
    +       ...     ret = df.assign(v=(v - v.mean()) / v.std())
    +       >>> df.groupby('id').apply(normalize).show() # doctest: + SKIP
    +      +---+-------------------+
    +      | id|                  v|
    +      +---+-------------------+
    +      |  1|-0.7071067811865475|
    +      |  1| 0.7071067811865475|
    +      |  2|-0.7071067811865475|
    +      |  2| 0.7071067811865475|
    +      +---+-------------------+
    --- End diff --
    
    This produces Python doc output as below:
    
    <img width="455" alt="2017-10-01 10 34 24" 
src="https://user-images.githubusercontent.com/6477701/31054996-b6f5737a-a6f8-11e7-9559-239ab74b1cb4.png";>
    
    Sounds related with:
    
    ```
    spark/python/pyspark/sql/functions.py:docstring of 
pyspark.sql.functions.pandas_udf:46: WARNING: Enumerated list ends without a 
blank line; unexpected unindent.
    ```
    
    warning above.


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