Improved _from_dense method

Author: ankane

pgvector/sparsevec.py

@@ -137,8 +137,13 @@ def _from_sparse(self, arr: sparray | spmatrix, /) -> None:
 
     def _from_dense(self, value: list[float] | ndarray, /) -> None:
         self._dim = len(value)
-        self._indices = [i for i, v in enumerate(value) if v != 0]
-        self._values = [float(value[i]) for i in self._indices]
+        self._indices = []
+        self._values = []
+        for i, v in enumerate(value):
+            v = float(v)
+            if v != 0:
+                self._indices.append(i)
+                self._values.append(v)
 
     def _validate(self) -> None:
         if self._dim < 0: