bpo-37049: PEP 589: Add TypedDict to typing module (GH-13573)
The implementation is straightforward and essentially is just copied from `typing_extensions`.
diff --git a/Lib/typing.py b/Lib/typing.py
index 1044cc4..d3e84cd 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -89,6 +89,7 @@
'Set',
'FrozenSet',
'NamedTuple', # Not really a type.
+ 'TypedDict', # Not really a type.
'Generator',
# One-off things.
@@ -1490,6 +1491,89 @@
return _make_nmtuple(typename, fields)
+def _dict_new(cls, *args, **kwargs):
+ return dict(*args, **kwargs)
+
+
+def _typeddict_new(cls, _typename, _fields=None, **kwargs):
+ total = kwargs.pop('total', True)
+ if _fields is None:
+ _fields = kwargs
+ elif kwargs:
+ raise TypeError("TypedDict takes either a dict or keyword arguments,"
+ " but not both")
+
+ ns = {'__annotations__': dict(_fields), '__total__': total}
+ try:
+ # Setting correct module is necessary to make typed dict classes pickleable.
+ ns['__module__'] = sys._getframe(1).f_globals.get('__name__', '__main__')
+ except (AttributeError, ValueError):
+ pass
+
+ return _TypedDictMeta(_typename, (), ns)
+
+
+def _check_fails(cls, other):
+ # Typed dicts are only for static structural subtyping.
+ raise TypeError('TypedDict does not support instance and class checks')
+
+
+class _TypedDictMeta(type):
+ def __new__(cls, name, bases, ns, total=True):
+ """Create new typed dict class object.
+
+ This method is called directly when TypedDict is subclassed,
+ or via _typeddict_new when TypedDict is instantiated. This way
+ TypedDict supports all three syntax forms described in its docstring.
+ Subclasses and instances of TypedDict return actual dictionaries
+ via _dict_new.
+ """
+ ns['__new__'] = _typeddict_new if name == 'TypedDict' else _dict_new
+ tp_dict = super(_TypedDictMeta, cls).__new__(cls, name, (dict,), ns)
+
+ anns = ns.get('__annotations__', {})
+ msg = "TypedDict('Name', {f0: t0, f1: t1, ...}); each t must be a type"
+ anns = {n: _type_check(tp, msg) for n, tp in anns.items()}
+ for base in bases:
+ anns.update(base.__dict__.get('__annotations__', {}))
+ tp_dict.__annotations__ = anns
+ if not hasattr(tp_dict, '__total__'):
+ tp_dict.__total__ = total
+ return tp_dict
+
+ __instancecheck__ = __subclasscheck__ = _check_fails
+
+
+class TypedDict(dict, metaclass=_TypedDictMeta):
+ """A simple typed namespace. At runtime it is equivalent to a plain dict.
+
+ TypedDict creates a dictionary type that expects all of its
+ instances to have a certain set of keys, where each key is
+ associated with a value of a consistent type. This expectation
+ is not checked at runtime but is only enforced by type checkers.
+ Usage::
+
+ class Point2D(TypedDict):
+ x: int
+ y: int
+ label: str
+
+ a: Point2D = {'x': 1, 'y': 2, 'label': 'good'} # OK
+ b: Point2D = {'z': 3, 'label': 'bad'} # Fails type check
+
+ assert Point2D(x=1, y=2, label='first') == dict(x=1, y=2, label='first')
+
+ The type info can be accessed via Point2D.__annotations__. TypedDict
+ supports two additional equivalent forms::
+
+ Point2D = TypedDict('Point2D', x=int, y=int, label=str)
+ Point2D = TypedDict('Point2D', {'x': int, 'y': int, 'label': str})
+
+ The class syntax is only supported in Python 3.6+, while two other
+ syntax forms work for Python 2.7 and 3.2+
+ """
+
+
def NewType(name, tp):
"""NewType creates simple unique types with almost zero
runtime overhead. NewType(name, tp) is considered a subtype of tp