Create hnswlib.py

Added `LazyIndex` with the same API as `Index`.
Useful when having multiple indices with lazy initialization.

python_bindings/hnswlib.py

@@ -0,0 +1,38 @@
+import hnswlib
+
+class LazyIndex(hnswlib.Index):
+    def __init__(self, space, dim,max_elements=1024, ef_construction=200, M=16):
+        super().__init__(space, dim)
+        self.init_max_elements=max_elements
+        self.init_ef_construction=ef_construction
+        self.init_M=M
+    def init(self, max_elements=0):
+        if max_elements==0:
+            max_elements=self.init_max_elements
+        super().init_index(max_elements, self.init_M, self.init_ef_construction)
+    def add_items(self, data, ids=None, num_threads=-1):
+        if self.max_elements==0:
+            self.init()
+        return super().add_items(data,ids, num_threads)
+    def get_items(self, ids=None):
+        if self.max_elements==0:
+            return []
+        return super().get_items(ids)
+    def knn_query(self, data,k=1, num_threads=-1):
+        if self.max_elements==0:
+            return [], []
+        return super().knn_query(data, k, num_threads)
+    def resize_index(self, size):
+        if self.max_elements==0:
+            return self.init(size)
+        else:
+            return super().resize_index(size)
+    def set_ef(self, ef):
+        if self.max_elements==0:
+            self.init_ef_construction=ef
+            return
+        super().set_ef(ef)
+    def get_max_elements(self):
+        return self.max_elements
+    def get_current_count(self):
+        return self.element_count