From 8e43ca9ffa05e64fa8478e1bce8a18c26dbc4cb5 Mon Sep 17 00:00:00 2001
From: Kelsey Jordahl <kjordahl@enthought.com>
Date: Fri, 28 Jun 2013 22:11:01 -0400
Subject: [PATCH] Symmetric union operation

---
 geopandas/geoseries.py  | 24 +++++++++---------------
 tests/test_geoseries.py | 12 ++++++++++++
 2 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/geopandas/geoseries.py b/geopandas/geoseries.py
index 026346f..aa40ca9 100644
--- a/geopandas/geoseries.py
+++ b/geopandas/geoseries.py
@@ -161,32 +161,26 @@ class GeoSeries(Series):
             return Series([s.contains(other) for s in self],
                           index=self.index)
 
-    # TODO: refactor to eliminate replications
     def difference(self, other):
         """
         Return a GeoSeries of differences
         Operates on either a GeoSeries or a Shapely geometry
         """
-        if isinstance(other, GeoSeries):
-            # TODO: align series
-            return GeoSeries([s[0].difference(s[1]) for s in zip(self, other)],
-                          index=self.index)
-        else:
-            return GeoSeries([s.difference(other) for s in self],
-                          index=self.index)
+        return self._geo_op(other, 'difference')
+
+    def symmetric_difference(self, other):
+        """
+        Return a GeoSeries of differences
+        Operates on either a GeoSeries or a Shapely geometry
+        """
+        return self._geo_op(other, 'symmetric_difference')
 
     def union(self, other):
         """
         Return a GeoSeries of unions
         Operates on either a GeoSeries or a Shapely geometry
         """
-        if isinstance(other, GeoSeries):
-            # TODO: align series
-            return GeoSeries([s[0].union(s[1]) for s in zip(self, other)],
-                          index=self.index)
-        else:
-            return GeoSeries([s.union(other) for s in self],
-                          index=self.index)
+        return self._geo_op(other, 'union')
 
     def buffer(self, distance, resolution=16):
         return GeoSeries([geom.buffer(distance, resolution) for geom in self],
diff --git a/tests/test_geoseries.py b/tests/test_geoseries.py
index 844407e..c4dd462 100644
--- a/tests/test_geoseries.py
+++ b/tests/test_geoseries.py
@@ -12,6 +12,8 @@ class TestSeries(unittest.TestCase):
         self.sq = Polygon([(0, 0), (1, 0), (1, 1), (0, 1)])
         self.g1 = GeoSeries([self.t1, self.sq])
         self.g2 = GeoSeries([self.sq, self.t1])
+        self.g3 = GeoSeries([self.t1, self.t2])
+        self.g4 = GeoSeries([self.t2, self.t1])
 
     def test_area(self):
         assert np.allclose(self.g1.area.values, np.array([0.5, 1.0]))
@@ -43,6 +45,16 @@ class TestSeries(unittest.TestCase):
         assert u[0].is_empty
         assert u[1].equals(self.t2)
 
+    def test_symmetric_difference_series(self):
+        u = self.g3.symmetric_difference(self.g4)
+        assert u[0].equals(self.sq)
+        assert u[1].equals(self.sq)
+
+    def test_symmetric_difference_poly(self):
+        u = self.g3.symmetric_difference(self.t1)
+        assert u[0].is_empty
+        assert u[1].equals(self.sq)
+
     def test_difference_poly(self):
         u = self.g1.difference(self.t2)
         assert u[0].equals(self.t1)