feat: add support for namedtuple type

changes/1324-PrettyWood.md

@@ -0,0 +1 @@
+add basic support for `namedtuple` type

docs/usage/types.md

@@ -54,6 +54,15 @@ with custom properties and validation.
 : allows `list`, `tuple`, `set`, `frozenset`, `deque`, or generators and casts to a deque;
   see `typing.Deque` below for sub-type constraints
 
+`namedtuple`
+: Same as `tuple` but instantiates with the given namedtuple
+
+!!! warning
+    _pydantic_ doesn't validate the type of the fields inside the `namedtuple`!
+    Even if you use `typing.NamedTuple` and declare the expected types, _pydantic_ will just
+    make sure you get an instance of `namedtuple`.
+    Please use a `BaseModel` or `dataclass` if you expect validation
+
 `datetime.date`
 : see [Datetime Types](#datetime-types) below for more detail on parsing and validation
 

pydantic/typing.py

@@ -155,6 +155,7 @@ def get_args(tp: Type[Any]) -> Tuple[Any, ...]:
     'is_literal_type',
     'literal_values',
     'Literal',
+    'is_namedtuple_class',
     'is_new_type',
     'new_type_supertype',
     'is_classvar',
@@ -258,6 +259,13 @@ def all_literal_values(type_: Type[Any]) -> Tuple[Any, ...]:
     return tuple(x for value in values for x in all_literal_values(value))
 
 
+def is_namedtuple_class(type_: Type[Any]) -> bool:
+    try:
+        return issubclass(type_, tuple) and hasattr(type_, '_fields')
+    except TypeError:
+        return False
+
+
 test_type = NewType('test_type', str)
 
 

pydantic/validators.py

@@ -15,6 +15,7 @@
     FrozenSet,
     Generator,
     List,
+    NamedTuple,
     Pattern,
     Set,
     Tuple,
@@ -34,6 +35,7 @@
     get_class,
     is_callable_type,
     is_literal_type,
+    is_namedtuple_class,
 )
 from .utils import almost_equal_floats, lenient_issubclass, sequence_like
 
@@ -523,6 +525,16 @@ def pattern_validator(v: Any) -> Pattern[str]:
         raise errors.PatternError()
 
 
+N = TypeVar('N', bound=NamedTuple)
+
+
+def make_namedtuple_validator(namedtuple_type: Type[N]) -> Callable[[Tuple[Any, ...]], N]:
+    def namedtuple_validator(v: Tuple[Any, ...]) -> N:
+        return namedtuple_type(*v)
+
+    return namedtuple_validator
+
+
 class IfConfig:
     def __init__(self, validator: AnyCallable, *config_attr_names: str) -> None:
         self.validator = validator
@@ -610,6 +622,10 @@ def find_validators(  # noqa: C901 (ignore complexity)
     if type_ is IntEnum:
         yield int_enum_validator
         return
+    if is_namedtuple_class(type_):
+        yield tuple_validator
+        yield make_namedtuple_validator(type_)
+        return
 
     class_ = get_class(type_)
     if class_ is not None:

tests/test_validators.py

@@ -1,7 +1,7 @@
-from collections import deque
+from collections import deque, namedtuple
 from datetime import datetime
 from itertools import product
-from typing import Dict, List, Optional, Tuple
+from typing import Dict, List, NamedTuple, Optional, Tuple
 
 import pytest
 
@@ -1211,3 +1211,23 @@ def validate_foo(cls, v):
     with pytest.raises(RuntimeError, match='test error'):
         model.foo = 'raise_exception'
     assert model.foo == 'foo'
+
+
+def test_namedtuple():
+    Position = namedtuple('Pos', 'x y')
+
+    class Event(NamedTuple):
+        a: int
+        b: int
+        c: str
+
+    class Model(BaseModel):
+        pos: Position
+        events: List[Event]
+
+    model = Model(pos=(1, 2), events=[[1, 2, 'qwe']])
+    assert isinstance(model.pos, Position)
+    assert isinstance(model.events[0], Event)
+    assert model.pos.x == 1
+    assert model.events[0].c == 'qwe'
+    assert repr(model) == "Model(pos=Pos(x=1, y=2), events=[Event(a=1, b=2, c='qwe')])"