Prevent get_coordinate_pointers from mutating input coordinates

[sjones94549]

Index.get_coordinate_pointers(coordinates) converts point-inputs to bounding boxes. However, it does so using the += operator, which has the unfortunate side effect of mutating list inputs, and breaking with numpy arrays (which sum with += rather than appending). This change switches from += to = to prevent input-mutation, and uses coordinates = *coordinates, *coordinates for numpy compatibility.

Before

In [1]: import numpy as np
   ...: import rtree
   ...:
   ...: boxes15 = np.genfromtxt('boxes_15x15.data')
   ...: idx = rtree.index.Index()
   ...: for i, coords in enumerate(boxes15):
   ...:     idx.add(i, coords)

In [2]: # Tuples work and are not mutated (good)
   ...: point = 64, 64
   ...: list(idx.intersection(point))
Out[2]: [4, 53]

In [3]: point
Out[3]: (64, 64)

In [4]: # Lists work but are mutated (bad)
   ...: point = [64, 64]
   ...: list(idx.intersection(point))
Out[4]: [4, 53]

In [5]: point
Out[5]: [64, 64, 64, 64]  # <-- Mutated

In [6]: # Numpy arrays don't work (and would also be mutated) (bad)
   ...: point = np.array([64, 64])
   ...: idx.intersection(point)  # Breaks because `+=` sums in numpy rather than appends
---------------------------------------------------------------------------
RTreeError                                Traceback (most recent call last)
<ipython-input-6-1051681b49f7> in <module>
      1 point = np.array([64, 64])
----> 2 idx.intersection(point)  # Breaks because `+=` sums in numpy rather than appends

~/opt/anaconda3/envs/rtree/lib/python3.8/site-packages/rtree/index.py in intersection(self, coordinates, objects)
    675             return self._intersection_obj(coordinates, objects)
    676
--> 677         p_mins, p_maxs = self.get_coordinate_pointers(coordinates)
    678
    679         p_num_results = ctypes.c_uint64(0)

~/opt/anaconda3/envs/rtree/lib/python3.8/site-packages/rtree/index.py in get_coordinate_pointers(self, coordinates)
    342
    343         if len(coordinates) != dimension * 2:
--> 344             raise core.RTreeError(
    345                 "Coordinates must be in the form "
    346                 "(minx, miny, maxx, maxy) or (x, y) for 2D indexes")

RTreeError: Coordinates must be in the form (minx, miny, maxx, maxy) or (x, y) for 2D indexes

After

In [1]: import numpy as np
   ...: import rtree
   ...:
   ...: boxes15 = np.genfromtxt('boxes_15x15.data')
   ...: idx = rtree.index.Index()
   ...: for i, coords in enumerate(boxes15):
   ...:     idx.add(i, coords)

In [2]: point = 64, 64
   ...: list(idx.intersection(point))
Out[2]: [4, 53]

In [3]: point
Out[3]: (64, 64)

In [4]: point = [64, 64]
   ...: list(idx.intersection(point))
Out[4]: [4, 53]

In [5]: point
Out[5]: [64, 64]

In [6]: point = np.array([64, 64])

In [7]: list(idx.intersection(point))
Out[7]: [4, 53]

In [8]: point
Out[8]: array([64, 64])

[sjones94549]

@hobu thoughts? If worthwhile, should I add a test similar to:

diff --git a/tests/test_index.py b/tests/test_index.py
index c3ac97a..d9ab209 100644
--- a/tests/test_index.py
+++ b/tests/test_index.py
@@ -260,6 +260,20 @@ class IndexIntersection(IndexTestCase):

         self.assertEqual([1, 1], list(idx.intersection((0, 0, 5, 5))))

+    def test_point_intersection(self):
+        """Using a point returns expected hits"""
+        point = 64, 64
+        self.assertEqual([4, 53], list(self.idx.intersection(point)))
+        self.assertEqual((64, 64), point)
+
+        point = [64, 64]
+        self.assertEqual([4, 53], list(self.idx.intersection(point)))
+        self.assertEqual([64, 64], point)
+
+        point = np.array([64, 64])
+        self.assertEqual([4, 53], list(self.idx.intersection(point)))
+        self.assertTrue(np.array_equal(np.array([64, 64]), point))
+

...or perhaps intersection() doesn't support points?

[hobu]

The tests would be fine, although point-wise intersection hasn't been a promised feature of this library.

[sjones94549]

The tests would be fine, although point-wise intersection hasn't been a promised feature of this library.

In that case, I'll leave the test out. I do find point-wise intersections useful, but will do so at my own risk 😀