Github user HyukjinKwon commented on a diff in the pull request:
https://github.com/apache/spark/pull/18659#discussion_r139592201
--- Diff: python/pyspark/sql/functions.py ---
@@ -2142,18 +2159,26 @@ def udf(f=None, returnType=StringType()):
| 8| JOHN DOE| 22|
+----------+--------------+------------+
"""
- def _udf(f, returnType=StringType()):
- udf_obj = UserDefinedFunction(f, returnType)
- return udf_obj._wrapped()
+ return _create_udf(f, returnType=returnType, vectorized=False)
- # decorator @udf, @udf() or @udf(dataType())
- if f is None or isinstance(f, (str, DataType)):
- # If DataType has been passed as a positional argument
- # for decorator use it as a returnType
- return_type = f or returnType
- return functools.partial(_udf, returnType=return_type)
+
+@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.
+
+ :param f: python function if used as a standalone function
+ :param returnType: a :class:`pyspark.sql.types.DataType` object
+
+ # TODO: doctest
+ """
+ import inspect
+ # If function "f" does not define the optional kwargs, then wrap with
a kwargs placeholder
+ if inspect.getargspec(f).keywords is None:
+ return _create_udf(lambda *a, **kwargs: f(*a),
returnType=returnType, vectorized=True)
--- End diff --
How about disallowing it for now? I think it could be an option if
0-parameter UDF alone should not be supported consistently. `return
pd.Series(1).repeat(kwargs['length'])` looks still a little bit weird ..
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