add parse_obj

layercake/layercake/dynamodb.py

@@ -5,7 +5,7 @@ from base64 import urlsafe_b64decode, urlsafe_b64encode
 from dataclasses import dataclass
 from datetime import datetime
 from ipaddress import IPv4Address
-from typing import TYPE_CHECKING, Any, Type, TypedDict
+from typing import TYPE_CHECKING, Any, Self, Type, TypedDict
 from urllib.parse import quote, unquote
 from uuid import UUID
 
@@ -251,6 +251,19 @@ class KeyPair(Key):
             ':sk': self[SK],
         }
 
+    @classmethod
+    def parse_obj(cls, obj: Any) -> Self | None:
+        if not obj:
+            return None
+
+        match obj:
+            case dict():
+                pair = obj.values()
+            case _:
+                pair = obj
+
+        return cls(*pair)
+
 
 class TransactItems:
     def __init__(self, table_name: str) -> None:

layercake/tests/test_dynamodb.py

@@ -75,6 +75,10 @@ def test_keypair():
     assert KeyPair('123', 'abc').expr_attr_name() == {'#pk': 'id', '#sk': 'sk'}
     assert KeyPair('123', 'abc').expr_attr_values() == {':pk': '123', ':sk': 'abc'}
 
+    assert KeyPair.parse_obj({'id': '123', 'sk': 'abc'}) == {'id': '123', 'sk': 'abc'}
+    assert KeyPair.parse_obj(['123', 'abc']) == {'id': '123', 'sk': 'abc'}
+    assert KeyPair.parse_obj([]) is None
+
 
 def test_prefixkey():
     key = PrefixKey('emails')