DOC: Improve docs (GH19312) for Series.nonzero() (#19324)

Author: drorata

pandas/core/series.py

@@ -481,7 +481,7 @@ def compress(self, condition, *args, **kwargs):
 
     def nonzero(self):
         """
-        Return the indices of the elements that are non-zero
+        Return the *integer* indices of the elements that are non-zero
 
         This method is equivalent to calling `numpy.nonzero` on the
         series data. For compatibility with NumPy, the return value is
@@ -499,6 +499,15 @@ def nonzero(self):
         3    4
         dtype: int64
 
+        >>> s = pd.Series([0, 3, 0, 4], index=['a', 'b', 'c', 'd'])
+        # same return although index of s is different
+        >>> s.nonzero()
+        (array([1, 3]),)
+        >>> s.iloc[s.nonzero()[0]]
+        b    3
+        d    4
+        dtype: int64
+
         See Also
         --------
         numpy.nonzero