Fixed error parsing zero sparse vectors

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## 0.3.1 (unreleased)
 
+- Fixed error parsing zero sparse vectors
 - Fixed error with Psycopg 2 and pgvector < 0.7
 - Fixed error message when `vector` type not found with Psycopg 3
 

pgvector/utils/sparsevec.py

@@ -95,10 +95,12 @@ def from_text(cls, value):
         elements, dim = value.split('/', 2)
         indices = []
         values = []
-        for e in elements[1:-1].split(','):
-            i, v = e.split(':', 2)
-            indices.append(int(i) - 1)
-            values.append(float(v))
+        # split on empty string returns single element list
+        if len(elements) > 2:
+            for e in elements[1:-1].split(','):
+                i, v = e.split(':', 2)
+                indices.append(int(i) - 1)
+                values.append(float(v))
         return cls._from_parts(int(dim), indices, values)
 
     @classmethod

tests/test_sparse_vector.py

@@ -63,3 +63,7 @@ def test_values(self):
 
     def test_to_coo(self):
         assert SparseVector([1, 0, 2, 0, 3, 0]).to_coo().toarray().tolist() == [[1, 0, 2, 0, 3, 0]]
+
+    def test_zero_vector_text(self):
+        vec = SparseVector({}, 3)
+        assert vec.to_list() == SparseVector.from_text(vec.to_text()).to_list()