Allow printing of instance resources in flatdata-py (#216)

Fixes #128

Signed-off-by: Christian Vetter <[email protected]>

flatdata-py/flatdata/lib/resources.py

@@ -99,10 +99,10 @@ def __getitem__(self, index):
         if isinstance(index, slice):
             return _VectorSlice(index, self)
 
-        if index >= self._size:
-            raise IndexError("Vector access out of bounds")
         if index < 0:
             index += len(self)
+        if index >= self._size or index < 0:
+            raise IndexError("Vector access out of bounds")
         return self._get_item(index)
 
     def __iter__(self):
@@ -173,6 +173,21 @@ def __getitem__(self, item):
 
 
 class Instance(ResourceBase):
+    def __getitem__(self, index):
+        if isinstance(index, slice):
+            raise IndexError("Instance has only one item")
+
+        if index < 0:
+            index += 1
+        if index >= 1 or index < 0:
+            raise IndexError("Instance access out of bounds")
+
+        return self._get_item(index)
+
+    def __iter__(self):
+        for i in range(1):
+            yield self._get_item(i)
+
     def __getattr__(self, name):
         offset = self._item_offset(0)
         return getattr(self._element_type(self._mem, offset), name)

flatdata-py/tests/test_backward_compatibility.py

@@ -26,6 +26,7 @@ def test_instance_reading():
     }
     archive = module.backward_compatibility_Archive(DictResourceStorage(valid_data))
     check_signed_struct(archive.resource)
+    check_signed_struct(archive.resource[0])
 
 
 def test_vector_reading():