Support ORM objects to 'parse_obj', replace #520

pydantic/main.py

@@ -14,7 +14,6 @@
     Dict,
     Generator,
     List,
-    Mapping,
     Optional,
     Set,
     Tuple,
@@ -313,13 +312,16 @@ def json(
         )
 
     @classmethod
-    def parse_obj(cls: Type['Model'], obj: Mapping[Any, Any]) -> 'Model':
+    def parse_obj(cls: Type['Model'], obj: Any) -> 'Model':
         if not isinstance(obj, dict):
-            try:
-                obj = dict(obj)
-            except (TypeError, ValueError) as e:
-                exc = TypeError(f'{cls.__name__} expected dict not {type(obj).__name__}')
-                raise ValidationError([ErrorWrapper(exc, loc='__obj__')]) from e
+            if hasattr(obj, '__iter__'):
+                try:
+                    obj = dict(obj)
+                except (TypeError, ValueError) as e:
+                    exc = TypeError(f'{cls.__name__} expected dict not {type(obj).__name__}')
+                    raise ValidationError([ErrorWrapper(exc, loc='__obj__')]) from e
+            else:
+                obj = cls._decompose_class(obj)
         return cls(**obj)
 
     @classmethod
@@ -421,14 +423,21 @@ def __get_validators__(cls) -> 'CallableGenerator':
         yield cls.validate
 
     @classmethod
-    def validate(cls: Type['Model'], value: Union['DictStrAny', 'Model']) -> 'Model':
+    def validate(cls: Type['Model'], value: Any) -> 'Model':
         if isinstance(value, dict):
             return cls(**value)
         elif isinstance(value, cls):
             return value.copy()
-        else:
+        elif hasattr(value, '__iter__'):
             with change_exception(DictError, TypeError, ValueError):
-                return cls(**dict(value))  # type: ignore
+                return cls(**dict(value))
+        else:
+            with change_exception(DictError, TypeError, ValueError, AttributeError):
+                return cls(**cls._decompose_class(value))
+
+    @classmethod
+    def _decompose_class(cls, obj: Any) -> 'DictStrAny':
+        return obj.__dict__
 
     @classmethod
     def _get_value(cls, v: Any, by_alias: bool, skip_defaults: bool) -> Any:

tests/test_edge_cases.py

@@ -874,3 +874,37 @@ class Spam(BaseModel):
     assert Spam(c=Foo(a='123')).dict() == {'c': {'a': 123}}
     with pytest.raises(ValidationError):
         Spam(c=Bar(b='123'))
+
+
+def test_orm_mode():
+    class PetCls:
+        def __init__(self, *, name: str, species: str):
+            self.name = name
+            self.species = species
+
+    class PersonCls:
+        def __init__(self, *, name: str, age: float = None, pets: List[PetCls]):
+            self.name = name
+            self.age = age
+            self.pets = pets
+
+    class Pet(BaseModel):
+        name: str
+        species: str
+
+    class Person(BaseModel):
+        name: str
+        age: float = None
+        pets: List[Pet]
+
+    bones = PetCls(name='Bones', species='dog')
+    orion = PetCls(name='Orion', species='cat')
+    alice = PersonCls(name='Alice', age=20, pets=[bones, orion])
+
+    alice_model = Person.parse_obj(alice)
+
+    assert alice_model.dict() == {
+        'name': 'Alice',
+        'pets': [{'name': 'Bones', 'species': 'dog'}, {'name': 'Orion', 'species': 'cat'}],
+        'age': 20.0,
+    }