Optionally exclude input geom from results (#1166)

* Optionally exclude input geom from results

Resolves #1106

* exclusive instead of exclude_geom

CHANGES.txt

@@ -10,6 +10,8 @@ Shapely 1.8 will support only Python versions >= 3.6.
 
 New features:
 
+- The STRtree nearest*() methods now take an optional argument that
+  specifies exclusion of the input geometry from results (#1115).
 - A GeometryTypeError has been added to shapely.errors and is consistently
   raised instead of TypeError or ValueError as in version 1.7. For backwards
   compatibility, the new exception will derive from TypeError and Value error

shapely/strtree.py

@@ -21,6 +21,7 @@
 import ctypes
 import logging
 from typing import Any, ItemsView, Iterable, Iterator, Sequence, Tuple, Union
+import sys
 from warnings import warn
 
 from shapely.errors import ShapelyDeprecationWarning
@@ -249,7 +250,9 @@ def query(self, geom: BaseGeometry) -> Sequence[BaseGeometry]:
         """
         return self.query_geoms(geom)
 
-    def nearest_item(self, geom: BaseGeometry) -> Union[Any, None]:
+    def nearest_item(
+        self, geom: BaseGeometry, exclusive: bool = False
+    ) -> Union[Any, None]:
         """Query the tree for the node nearest to geom and get the item
         stored in the node.
 
@@ -259,6 +262,9 @@ def nearest_item(self, geom: BaseGeometry) -> Union[Any, None]:
         ----------
         geom : geometry object
             The query geometry.
+        exclusive : bool, optional
+            Whether to exclude the item corresponding to the given geom
+            from results or not.  Default: False.
 
         Returns
         -------
@@ -289,10 +295,14 @@ def nearest_item(self, geom: BaseGeometry) -> Union[Any, None]:
 
         def callback(item1, item2, distance, userdata):
             try:
+                callback_userdata = ctypes.cast(userdata, ctypes.py_object).value
                 idx = ctypes.cast(item1, ctypes.py_object).value
                 geom2 = ctypes.cast(item2, ctypes.py_object).value
                 dist = ctypes.cast(distance, ctypes.POINTER(ctypes.c_double))
-                lgeos.GEOSDistance(self._rev[idx]._geom, geom2._geom, dist)
+                if callback_userdata["exclusive"] and self._rev[idx].equals(geom2):
+                    dist[0] = sys.float_info.max
+                else:
+                    lgeos.GEOSDistance(self._rev[idx]._geom, geom2._geom, dist)
                 return 1
             except Exception:
                 log.exception("Caught exception")
@@ -303,19 +313,24 @@ def callback(item1, item2, distance, userdata):
             ctypes.py_object(geom),
             envelope._geom,
             lgeos.GEOSDistanceCallback(callback),
-            None,
+            ctypes.py_object({"exclusive": exclusive}),
         )
         result = ctypes.cast(item, ctypes.py_object).value
         return result
 
-    def nearest_geom(self, geom: BaseGeometry) -> Union[BaseGeometry, None]:
+    def nearest_geom(
+        self, geom: BaseGeometry, exclusive: bool = False
+    ) -> Union[BaseGeometry, None]:
         """Query the tree for the node nearest to geom and get the
         geometry corresponding to the item stored in the node.
 
         Parameters
         ----------
         geom : geometry object
             The query geometry.
+        exclusive : bool, optional
+            Whether to exclude the given geom from results or not.
+            Default: False.
 
         Returns
         -------
@@ -325,13 +340,15 @@ def nearest_geom(self, geom: BaseGeometry) -> Union[BaseGeometry, None]:
         version 2.0.
 
         """
-        item = self.nearest_item(geom)
+        item = self.nearest_item(geom, exclusive=exclusive)
         if item is None:
             return None
         else:
             return self._rev[item]
 
-    def nearest(self, geom: BaseGeometry) -> Union[BaseGeometry, None]:
+    def nearest(
+        self, geom: BaseGeometry, exclusive: bool = False
+    ) -> Union[BaseGeometry, None]:
         """Query the tree for the node nearest to geom and get the
         geometry corresponding to the item stored in the node.
 
@@ -342,6 +359,9 @@ def nearest(self, geom: BaseGeometry) -> Union[BaseGeometry, None]:
         ----------
         geom : geometry object
             The query geometry.
+        exclusive : bool, optional
+            Whether to exclude the given geom from results or not.
+            Default: False.
 
         Returns
         -------
@@ -351,4 +371,4 @@ def nearest(self, geom: BaseGeometry) -> Union[BaseGeometry, None]:
         version 2.0.
 
         """
-        return self.nearest_geom(geom)
+        return self.nearest_geom(geom, exclusive=exclusive)

tests/test_strtree.py

@@ -177,3 +177,22 @@ def test_nearest_items(geoms, items):
     with pytest.warns(ShapelyDeprecationWarning):
         tree = STRtree(geoms, items)
     assert tree.nearest_item(None) is None
+
+
+@pytest.mark.skipif(geos_version < (3, 6, 0), reason="GEOS 3.6.0 required")
+@pytest.mark.parametrize(
+    "geoms",
+    [
+        [
+            Point(0, 0.5),
+            Polygon([(1, 0), (2, 0), (2, 1), (1, 1)]),
+            Polygon([(0, 2), (1, 2), (1, 3), (0, 3)]),
+        ]
+    ],
+)
+@pytest.mark.parametrize("items", [list(range(1, 4)), list("abc")])
+@pytest.mark.parametrize("query_geom", [Point(0, 0.5)])
+def test_nearest_item_exclusive(geoms, items, query_geom):
+    with pytest.warns(ShapelyDeprecationWarning):
+        tree = STRtree(geoms, items)
+    assert tree.nearest_item(query_geom, exclusive=True) != items[0]