Implement Series.item

databricks/koalas/missing/series.py

@@ -53,7 +53,6 @@ class _MissingPandasLikeSeries(object):
     first = unsupported_function("first")
     infer_objects = unsupported_function("infer_objects")
     interpolate = unsupported_function("interpolate")
-    item = unsupported_function("item")
     items = unsupported_function("items")
     iteritems = unsupported_function("iteritems")
     last = unsupported_function("last")

databricks/koalas/series.py

@@ -4730,6 +4730,31 @@ def asof(self, where):
         result_series.name = self.name
         return result_series
 
+    def item(self):
+        """
+        Return the first element of the underlying data as a Python scalar.
+
+        Returns
+        -------
+        scalar
+            The first element of Series.
+
+        Raises
+        ------
+        ValueError
+            If the data is not length-1.
+
+        Examples
+        --------
+        >>> kser = ks.Series([10])
+        >>> kser.item()
+        10
+        """
+        item_top_two = self[:2]
+        if len(item_top_two) != 1:
+            raise ValueError("can only convert an array of size 1 to a Python scalar")
+        return item_top_two[0]
+
     def _cum(self, func, skipna, part_cols=()):
         # This is used to cummin, cummax, cumsum, etc.
 

databricks/koalas/tests/test_series.py

@@ -1520,3 +1520,7 @@ def test_shape(self):
         pser = kser.to_pandas()
 
         self.assert_eq(pser.shape, kser.shape)
+
+    def test_item(self):
+        kser = ks.Series([10, 20])
+        self.assertRaises(ValueError, lambda: kser.item())

docs/source/reference/series.rst

@@ -56,6 +56,7 @@ Indexing, iteration
    Series.iloc
    Series.keys
    Series.pop
+   Series.item
    Series.xs
    Series.get