Implement Series.update

databricks/koalas/missing/series.py

@@ -111,7 +111,6 @@ class _MissingPandasLikeSeries(object):
     tz_convert = unsupported_function('tz_convert')
     tz_localize = unsupported_function('tz_localize')
     unstack = unsupported_function('unstack')
-    update = unsupported_function('update')
     view = unsupported_function('view')
     where = unsupported_function('where')
     xs = unsupported_function('xs')

databricks/koalas/series.py

@@ -3409,6 +3409,66 @@ def replace(self, to_replace=None, value=None, regex=False) -> 'Series':
 
         return self._with_new_scol(current)
 
+    def update(self, other):
+        """
+        Modify Series in place using non-NA values from passed Series. Aligns on index.
+
+        Parameters
+        ----------
+        other : Series
+
+        Examples
+        --------
+        >>> s = ks.Series([1, 2, 3])
+        >>> s.update(ks.Series([4, 5, 6]))
+        >>> s
+        0    4
+        1    5
+        2    6
+        Name: 0, dtype: int64
+
+        >>> s = ks.Series(['a', 'b', 'c'])
+        >>> s.update(ks.Series(['d', 'e'], index=[0, 2]))
+        >>> s
+        0    d
+        1    b
+        2    e
+        Name: 0, dtype: object
+
+        >>> s = ks.Series([1, 2, 3])
+        >>> s.update(ks.Series([4, 5, 6, 7, 8]))
+        >>> s
+        0    4
+        1    5
+        2    6
+        Name: 0, dtype: int64
+
+        If ``other`` contains NaNs the corresponding values are not updated
+        in the original Series.
+
+        >>> s = ks.Series([1, 2, 3])
+        >>> s.update(ks.Series([4, np.nan, 6]))
+        >>> s
+        0    4.0
+        1    2.0
+        2    6.0
+        Name: 0, dtype: float64
+        """
+        if not isinstance(other, Series):
+            raise ValueError("'other' must be a Series")
+
+        self_sdf = self._internal.sdf
+        other_sdf = other._internal.sdf.limit(len(self))
+        temp_col = self.name + "_"
+        temp_idx = self._index_map[0][0]
+
+        other_temp = other_sdf.withColumn(temp_col, other_sdf[other.name])
+        new_sdf = self_sdf.join(other_temp, temp_idx, 'outer').sort(temp_idx)
+        cond = F.when(other_temp[temp_col].isNotNull(), other_temp[temp_col]) \
+                .otherwise(self._scol) \
+                .alias(self.name)
+        self._internal = _col(ks.DataFrame(_InternalFrame(sdf=new_sdf.select(cond))))._internal
+
     def _cum(self, func, skipna, part_cols=()):
         # This is used to cummin, cummax, cumsum, etc.
         index_columns = self._internal.index_columns

databricks/koalas/tests/test_series.py

@@ -728,3 +728,11 @@ def test_duplicates(self):
 
         self.assert_eq(pser.drop_duplicates().sort_values(),
                        kser.drop_duplicates().sort_values())
+
+    def test_update(self):
+        pser = pd.Series([10, 20, 15, 30, 45], name='x')
+        kser = ks.Series(pser)
+
+        msg = "'other' must be a Series"
+        with self.assertRaisesRegex(ValueError, msg):
+            kser.update(10)

docs/source/reference/series.rst

@@ -176,6 +176,7 @@ Combining / joining / merging
 
    Series.append
    Series.replace
+   Series.update
 
 Time series-related
 -------------------