Support pickle serialization for Grid objects

gridit/grid.py

@@ -76,6 +76,17 @@ def __hash__(self):
         """Return unique hash based on content."""
         return hash(tuple(self))
 
+    def __getstate__(self):
+        """Serialize object attributes for pickle dumps."""
+        state = dict(self)
+        if state["projection"] is None or state["projection"] == "":
+            del state["projection"]
+        return state
+
+    def __setstate__(self, state):
+        """Set object attributes from pickle loads."""
+        self.__init__(**state)
+
     def __eq__(self, other):
         """Return True if objects are equal."""
         if self.__class__.__name__ != other.__class__.__name__:

tests/test_grid.py

@@ -60,3 +60,34 @@ def test_grid_transform(grid_basic):
     from affine import Affine
 
     assert grid_basic.transform == Affine(10.0, 0.0, 1000.0, 0.0, -10.0, 2000.0)
+
+
+def test_pickle():
+    import pickle
+
+    # Without projection
+    grid = Grid(25.0, (36, 33), (1748725.0, 5449775.0))
+    expected_bytes = (
+        b"\x80\x04\x95c\x00\x00\x00\x00\x00\x00\x00\x8c\x0b"
+        b"gridit.grid\x94\x8c\x04Grid\x94\x93\x94)\x81\x94}\x94(\x8c\n"
+        b"resolution\x94G@9\x00\x00\x00\x00\x00\x00\x8c\x05"
+        b"shape\x94K$K!\x86\x94\x8c\x08"
+        b"top_left\x94GA:\xae\xf5\x00\x00\x00\x00GAT\xca\x0b\xc0\x00\x00\x00\x86"
+        b"\x94ub."
+    )
+    assert pickle.loads(expected_bytes) == grid, "failed loading previous serialization"
+    assert pickle.loads(pickle.dumps(grid)) == grid, "failed round-trip"
+
+    # With projection
+    grid = Grid(25.0, (36, 33), (1748725.0, 5449775.0), "EPSG:2193")
+    expected_bytes = (
+        b"\x80\x04\x95|\x00\x00\x00\x00\x00\x00\x00\x8c\x0b"
+        b"gridit.grid\x94\x8c\x04Grid\x94\x93\x94)\x81\x94}\x94(\x8c\n"
+        b"resolution\x94G@9\x00\x00\x00\x00\x00\x00\x8c\x05"
+        b"shape\x94K$K!\x86\x94\x8c\x08"
+        b"top_left\x94GA:\xae\xf5\x00\x00\x00\x00GAT\xca\x0b\xc0\x00\x00\x00\x86"
+        b"\x94\x8c\nprojection\x94\x8c\tEPSG:2193"
+        b"\x94ub."
+    )
+    assert pickle.loads(expected_bytes) == grid, "failed loading previous serialization"
+    assert pickle.loads(pickle.dumps(grid)) == grid, "failed round-trip"