Can we add comparison functions to Ltrees? (#668)

* Add some comparison tests
* Add some comparison tests
* Fix a bug
* Add comparison functions
* Add a load more tests

sqlalchemy_utils/primitives/ltree.py

@@ -206,3 +206,15 @@ def __unicode__(self):
 
     def __contains__(self, label):
         return label in self.path.split('.')
+
+    def __gt__(self, other):
+        return self.path > other.path
+
+    def __lt__(self, other):
+        return self.path < other.path
+
+    def __ge__(self, other):
+        return self.path >= other.path
+
+    def __le__(self, other):
+        return self.path <= other.path

tests/primitives/test_ltree.py

@@ -197,3 +197,21 @@ def test_repr(self):
     def test_str(self):
         ltree = Ltree('path.path')
         assert str(ltree) == 'path.path'
+
+    def test_lt(self):
+        assert Ltree('1') < Ltree('2')
+        assert Ltree('1.2.3') < Ltree('1.2.4')
+        assert Ltree('1.2.3') < Ltree('1.2.3.4')
+
+    def test_lte(self):
+        assert Ltree('1.2.3') <= Ltree('1.2.4')
+        assert Ltree('1') <= Ltree('1')
+
+    def test_gt(self):
+        assert Ltree('2') > Ltree('1')
+        assert Ltree('1.2.3') > Ltree('1.2.2')
+        assert Ltree('1.2.3.4') > Ltree('1.2.3')
+
+    def test_gte(self):
+        assert Ltree('1.2.3') >= Ltree('1.2.2')
+        assert Ltree('1') >= Ltree('1')