Python: Retain explicitly specified 'unique' with frac_as_map

python/src/exactextract/exact_extract.py

@@ -218,7 +218,11 @@ def prep_ops(stats, values, weights=None, *, add_unique=False):
             if op.stat == "unique":
                 del need_unique[op.key()]
         for op in need_unique.values():
-            ops += prepare_operations([change_stat(op, "unique")], values, weights)
+            for unique_op in prepare_operations(
+                [change_stat(op, "unique")], values, weights
+            ):
+                unique_op.name = "@delete@" + unique_op.name
+                ops.append(unique_op)
 
     return ops
 

python/src/exactextract/writer.py

@@ -29,7 +29,7 @@ def __init__(
 
         Args:
             array_type: type that should be used to represent array outputs.
-                        Either "numpy" (default) or "list".
+                        Either "numpy" (default), "list", or "set"
             map_fields: An optional dictionary of fields to be created by
                         interpreting one field as keys and another as values, in the format
                         ``{ dst_field : (src_keys, src_vals) }``. For example, the fields
@@ -38,24 +38,28 @@ def __init__(
         """
         super().__init__()
 
-        if array_type not in ("numpy", "list"):
+        if array_type not in ("numpy", "list", "set"):
             raise ValueError("Unsupported array_type: " + array_type)
 
         self.array_type = array_type
         self.feature_list = []
         self.map_fields = map_fields or {}
         self.op_fields = {}
         self.ops = []
+        self.remove_temporary_fields = False
 
     def add_operation(self, op):
         self.ops.append(op)
+        if op.name.startswith("@delete@"):
+            self.remove_temporary_fields = True
 
     def write(self, feature):
         f = JSONFeature()
         feature.copy_to(f)
 
-        self._convert_arrays(f)
         self._create_map_fields(f)
+        self._convert_arrays(f)
+        self._remove_temporary_fields(f)
 
         self.feature_list.append(f.feature)
 
@@ -71,6 +75,12 @@ def _convert_arrays(self, f):
             for k in props:
                 if type(props[k]) is np.ndarray:
                     props[k] = list(props[k])
+        elif self.array_type == "set":
+            import numpy as np
+
+            for k in props:
+                if type(props[k]) is np.ndarray:
+                    props[k] = set(props[k])
 
     def _fields_for_stat(self, stat):
         return [o.name for o in self.ops if o.stat == stat]
@@ -79,7 +89,6 @@ def _create_map_fields(self, f):
         props = f.feature["properties"]
 
         new_fields = {}
-        to_delete = set()
         for field in self.map_fields:
             key_stat, val_stat = self.map_fields[field]
 
@@ -99,12 +108,14 @@ def _create_map_fields(self, f):
                     k: v for k, v in zip(props[key_field], props[val_field])
                 }
 
-                to_delete.add(key_field)
-                to_delete.add(val_field)
-        for field in to_delete:
-            del props[field]
         props.update(new_fields)
 
+    def _remove_temporary_fields(self, f):
+        if self.remove_temporary_fields:
+            for field in list(f.feature["properties"]):
+                if field.startswith("@delete@"):
+                    del f.feature["properties"][field]
+
 
 class PandasWriter(Writer):
     """Creates a (Geo)Pandas DataFrame"""

python/src/pybindings/operation_bindings.cpp

@@ -126,7 +126,7 @@ bind_operation(py::module& m)
       .def("key", &Operation::key)
       .def("weighted", &Operation::weighted)
       .def_readonly("stat", &Operation::stat)
-      .def_readonly("name", &Operation::name)
+      .def_readwrite("name", &Operation::name)
       .def_readonly("values", &Operation::values)
       .def_readonly("weights", &Operation::weights);
 
@@ -135,7 +135,7 @@ bind_operation(py::module& m)
 
     m.def("prepare_operations", py::overload_cast<const std::vector<std::string>&, const std::vector<RasterSource*>&, const std::vector<RasterSource*>&>(&prepare_operations));
 
-    m.def("change_stat", [](const Operation& op, std::string stat) {
+    m.def("change_stat", [](const Operation& op, std::string_view stat) {
         auto sd = op.descriptor();
         sd.name = "";
         sd.stat = stat;

python/tests/test_exact_extract.py

@@ -1019,14 +1019,15 @@ def test_output_map_fields():
     result = exact_extract(
         rast,
         square,
-        ["frac", "weighted_frac"],
+        ["frac", "weighted_frac", "unique"],
         weights=weights,
-        output_options={"frac_as_map": True},
+        output_options={"frac_as_map": True, "array_type": "set"},
     )
 
     assert result[0]["properties"] == {
         "frac": {1: 0.25, 2: 0.5, 3: 0.1875, 4: 0.0625},
         "weighted_frac": {1: 0.0, 2: 0.0, 3: 0.75, 4: 0.25},
+        "unique": {1, 2, 3, 4},
     }