diff options
Diffstat (limited to 'Lib/typing.py')
| -rw-r--r-- | Lib/typing.py | 146 |
1 files changed, 133 insertions, 13 deletions
diff --git a/Lib/typing.py b/Lib/typing.py index 5573a1fbf9..6ce74fc9f1 100644 --- a/Lib/typing.py +++ b/Lib/typing.py @@ -6,6 +6,7 @@ import functools import re as stdlib_re # Avoid confusion with the re we export. import sys import types + try: import collections.abc as collections_abc except ImportError: @@ -17,6 +18,7 @@ __all__ = [ # Super-special typing primitives. 'Any', 'Callable', + 'ClassVar', 'Generic', 'Optional', 'Tuple', @@ -270,7 +272,7 @@ class _TypeAlias: def _get_type_vars(types, tvars): for t in types: - if isinstance(t, TypingMeta): + if isinstance(t, TypingMeta) or isinstance(t, _ClassVar): t._get_type_vars(tvars) @@ -281,7 +283,7 @@ def _type_vars(types): def _eval_type(t, globalns, localns): - if isinstance(t, TypingMeta): + if isinstance(t, TypingMeta) or isinstance(t, _ClassVar): return t._eval_type(globalns, localns) else: return t @@ -1114,6 +1116,67 @@ class Generic(metaclass=GenericMeta): return obj +class _ClassVar(metaclass=TypingMeta, _root=True): + """Special type construct to mark class variables. + + An annotation wrapped in ClassVar indicates that a given + attribute is intended to be used as a class variable and + should not be set on instances of that class. Usage:: + + class Starship: + stats: ClassVar[Dict[str, int]] = {} # class variable + damage: int = 10 # instance variable + + ClassVar accepts only types and cannot be further subscribed. + + Note that ClassVar is not a class itself, and should not + be used with isinstance() or issubclass(). + """ + + def __init__(self, tp=None, _root=False): + cls = type(self) + if _root: + self.__type__ = tp + else: + raise TypeError('Cannot initialize {}'.format(cls.__name__[1:])) + + def __getitem__(self, item): + cls = type(self) + if self.__type__ is None: + return cls(_type_check(item, + '{} accepts only types.'.format(cls.__name__[1:])), + _root=True) + raise TypeError('{} cannot be further subscripted' + .format(cls.__name__[1:])) + + def _eval_type(self, globalns, localns): + return type(self)(_eval_type(self.__type__, globalns, localns), + _root=True) + + def _get_type_vars(self, tvars): + if self.__type__: + _get_type_vars(self.__type__, tvars) + + def __repr__(self): + cls = type(self) + if not self.__type__: + return '{}.{}'.format(cls.__module__, cls.__name__[1:]) + return '{}.{}[{}]'.format(cls.__module__, cls.__name__[1:], + _type_repr(self.__type__)) + + def __hash__(self): + return hash((type(self).__name__, self.__type__)) + + def __eq__(self, other): + if not isinstance(other, _ClassVar): + return NotImplemented + if self.__type__ is not None: + return self.__type__ == other.__type__ + return self is other + +ClassVar = _ClassVar(_root=True) + + def cast(typ, val): """Cast a value to a type. @@ -1142,12 +1205,20 @@ def _get_defaults(func): def get_type_hints(obj, globalns=None, localns=None): - """Return type hints for a function or method object. + """Return type hints for an object. This is often the same as obj.__annotations__, but it handles forward references encoded as string literals, and if necessary adds Optional[t] if a default value equal to None is set. + The argument may be a module, class, method, or function. The annotations + are returned as a dictionary, or in the case of a class, a ChainMap of + dictionaries. + + TypeError is raised if the argument is not of a type that can contain + annotations, and an empty dictionary is returned if no annotations are + present. + BEWARE -- the behavior of globalns and localns is counterintuitive (unless you are familiar with how eval() and exec() work). The search order is locals first, then globals. @@ -1162,6 +1233,7 @@ def get_type_hints(obj, globalns=None, localns=None): - If two dict arguments are passed, they specify globals and locals, respectively. """ + if getattr(obj, '__no_type_check__', None): return {} if globalns is None: @@ -1170,16 +1242,62 @@ def get_type_hints(obj, globalns=None, localns=None): localns = globalns elif localns is None: localns = globalns - defaults = _get_defaults(obj) - hints = dict(obj.__annotations__) - for name, value in hints.items(): - if isinstance(value, str): - value = _ForwardRef(value) - value = _eval_type(value, globalns, localns) - if name in defaults and defaults[name] is None: - value = Optional[value] - hints[name] = value - return hints + + if (isinstance(obj, types.FunctionType) or + isinstance(obj, types.BuiltinFunctionType) or + isinstance(obj, types.MethodType)): + defaults = _get_defaults(obj) + hints = obj.__annotations__ + for name, value in hints.items(): + if value is None: + value = type(None) + if isinstance(value, str): + value = _ForwardRef(value) + value = _eval_type(value, globalns, localns) + if name in defaults and defaults[name] is None: + value = Optional[value] + hints[name] = value + return hints + + if isinstance(obj, types.ModuleType): + try: + hints = obj.__annotations__ + except AttributeError: + return {} + # we keep only those annotations that can be accessed on module + members = obj.__dict__ + hints = {name: value for name, value in hints.items() + if name in members} + for name, value in hints.items(): + if value is None: + value = type(None) + if isinstance(value, str): + value = _ForwardRef(value) + value = _eval_type(value, globalns, localns) + hints[name] = value + return hints + + if isinstance(object, type): + cmap = None + for base in reversed(obj.__mro__): + new_map = collections.ChainMap if cmap is None else cmap.new_child + try: + hints = base.__dict__['__annotations__'] + except KeyError: + cmap = new_map() + else: + for name, value in hints.items(): + if value is None: + value = type(None) + if isinstance(value, str): + value = _ForwardRef(value) + value = _eval_type(value, globalns, localns) + hints[name] = value + cmap = new_map(hints) + return cmap + + raise TypeError('{!r} is not a module, class, method, ' + 'or function.'.format(obj)) def no_type_check(arg): @@ -1300,6 +1418,8 @@ class _ProtocolMeta(GenericMeta): else: if (not attr.startswith('_abc_') and attr != '__abstractmethods__' and + attr != '__annotations__' and + attr != '__weakref__' and attr != '_is_protocol' and attr != '__dict__' and attr != '__args__' and |