dchvn commented on a change in pull request #34212:
URL: https://github.com/apache/spark/pull/34212#discussion_r794995636
##########
File path: python/pyspark/pandas/series.py
##########
@@ -4483,6 +4487,190 @@ def replace(
return self._with_new_scol(current) # TODO: dtype?
+ def combine(
+ self,
+ other: Union[Scalar, "Series"],
+ func: Callable,
+ fill_value: Optional[Any] = None,
+ ) -> "Series":
+ """
+ Combine the Series with a Series or scalar according to `func`.
+
+ Combine the Series and `other` using `func` to perform elementwise
+ selection for combined Series.
+ `fill_value` is assumed when value is missing at some index
+ from one of the two objects being combined.
+
+ .. versionadded:: 3.3.0
+
+ .. note:: This API executes the function once to infer the type which
is
+ potentially expensive, for instance, when the dataset is created
after
+ aggregations or sorting.
+
+ To avoid this, specify return type in ``func``, for instance, as
below:
+
+ >>> def multiply(x, y) -> np.int32:
+ ... return x * y
+
+ pandas-on-Spark uses return type hint and does not try to infer
the type.
+
+ This API does not support self combine for now.
+
+ >>> psser1 = ps.Series([1, 2, 3, 4])
+ >>> psser1.combine(psser1, max) # doctest: +SKIP
+ ...
+ ValueError: Unsupported self combine
+
+ Parameters
+ ----------
+ other : Series or scalar
+ The value(s) to be combined with the `Series`.
+ func : function
+ Function that takes two scalars as inputs and returns an element.
+ Note that type hint for return type is strongly recommended.
+ fill_value : scalar, optional
+ The value to assume when an index is missing from
+ one Series or the other. The default specifies to use the
+ appropriate NaN value for the underlying dtype of the Series.
+
+ Returns
+ -------
+ Series
+ The result of combining the Series with the other object.
+
+ See Also
+ --------
+ Series.combine_first : Combine Series values, choosing the calling
+ Series' values first.
+
+ Examples
+ --------
+ Consider 2 Datasets ``s1`` and ``s2`` containing
+ highest clocked speeds of different birds.
+
+ >>> from pyspark.pandas.config import set_option, reset_option
+ >>> set_option("compute.ops_on_diff_frames", True)
+ >>> s1 = ps.Series({'falcon': 330.0, 'eagle': 160.0})
+ >>> s1
+ falcon 330.0
+ eagle 160.0
+ dtype: float64
+ >>> s2 = ps.Series({'falcon': 345.0, 'eagle': 200.0, 'duck': 30.0})
+ >>> s2
+ falcon 345.0
+ eagle 200.0
+ duck 30.0
+ dtype: float64
+
+ Now, to combine the two datasets and view the highest speeds
+ of the birds across the two datasets
+
+ >>> def max_with_return_type(x, y) -> float:
+ ... return max(x, y)
+ ...
+ >>> s1.combine(s2, max_with_return_type)
+ duck NaN
+ eagle 200.0
+ falcon 345.0
+ dtype: float64
+
+ In the previous example, the resulting value for duck is missing,
+ because the maximum of a NaN and a float is a NaN.
+ So, in the example, we set ``fill_value=0``,
+ so the maximum value returned will be the value from some dataset.
+
+ >>> s1.combine(s2, max_with_return_type, fill_value=0)
+ duck 30.0
+ eagle 200.0
+ falcon 345.0
+ dtype: float64
+ >>> reset_option("compute.ops_on_diff_frames")
+ """
+ if not callable(func):
+ raise TypeError("'%s' object is not callable" %
type(func).__name__)
+
+ if pd.api.types.is_scalar(other): # type: ignore[attr-defined]
+ tmp_other_col =
verify_temp_column_name(self._internal.spark_frame, "__tmp_other_col__")
+ combined = self.to_frame()
+ combined[tmp_other_col] = other
+ combined = DataFrame(combined._internal.resolved_copy)
+ else:
+ assert isinstance(other, Series)
+ if same_anchor(self, other):
+ if self._column_label == other._column_label:
+ raise ValueError("Unsupported self combine")
+ combined = self._psdf[self._column_label, other._column_label]
+ elif fill_value is None:
+ combined = combine_frames(self.to_frame(), other.to_frame())
+ else:
+ combined = self._combine_frame_with_fill_value(other,
fill_value=fill_value)
+
+ try:
+ sig_return = infer_return_type(func)
+ if isinstance(sig_return, (UnknownType, DataFrameType)):
+ raise TypeError()
+ return_spark_type = sig_return.spark_type
+ return_dtype = sig_return.dtype
+ except (ValueError, TypeError):
+ # Here we execute with the first 1000 to get the return type.
+ # If the records were less than 1000, it uses pandas API directly
for a shortcut.
+ log_advice(
+ "If the type hints is not specified the `func` parameter for
`series.combine`, "
+ "it is expensive to infer the data type internally."
Review comment:
Oh, thank you!
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