✨ Create type that allows some values to be skipped in update and set

royalnet/alchemist/update.py

@@ -7,10 +7,32 @@ class Updatable:
     def update(self, **kwargs):
         """Set attributes from the kwargs, ignoring non-existant key/columns."""
         for key, value in kwargs.items():
+            if value is DoNotUpdate:
+                continue
             if hasattr(self, key):
                 setattr(self, key, value)
 
     def set(self, **kwargs):
         """Set attributes from the kwargs, without checking for non-existant key/columns."""
         for key, value in kwargs.items():
+            if value is DoNotUpdate:
+                continue
             setattr(self, key, value)
+
+
+class DoNotUpdateType:
+    """
+    A type, similar to NoneType, used to mark fields that should be skipped in update and set operations.
+    """
+    __slots__ = ()
+
+
+DoNotUpdate = DoNotUpdateType()
+"""The constant instance of the DoNotUpdateType."""
+
+
+__all__ = (
+    "Updatable",
+    "DoNotUpdateType",
+    "DoNotUpdate",
+)