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| author | AlexSm <alex@ydb.tech> | 2024-03-05 10:40:59 +0100 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2024-03-05 12:40:59 +0300 |
| commit | 1ac13c847b5358faba44dbb638a828e24369467b (patch) | |
| tree | 07672b4dd3604ad3dee540a02c6494cb7d10dc3d /contrib/tools/python3/Lib/typing.py | |
| parent | ffcca3e7f7958ddc6487b91d3df8c01054bd0638 (diff) | |
| download | ydb-1ac13c847b5358faba44dbb638a828e24369467b.tar.gz | |
Library import 16 (#2433)
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Diffstat (limited to 'contrib/tools/python3/Lib/typing.py')
| -rw-r--r-- | contrib/tools/python3/Lib/typing.py | 3438 |
1 files changed, 3438 insertions, 0 deletions
diff --git a/contrib/tools/python3/Lib/typing.py b/contrib/tools/python3/Lib/typing.py new file mode 100644 index 0000000000..ffe7ce8d8a --- /dev/null +++ b/contrib/tools/python3/Lib/typing.py @@ -0,0 +1,3438 @@ +""" +The typing module: Support for gradual typing as defined by PEP 484 and subsequent PEPs. + +Among other things, the module includes the following: +* Generic, Protocol, and internal machinery to support generic aliases. + All subscripted types like X[int], Union[int, str] are generic aliases. +* Various "special forms" that have unique meanings in type annotations: + NoReturn, Never, ClassVar, Self, Concatenate, Unpack, and others. +* Classes whose instances can be type arguments to generic classes and functions: + TypeVar, ParamSpec, TypeVarTuple. +* Public helper functions: get_type_hints, overload, cast, final, and others. +* Several protocols to support duck-typing: + SupportsFloat, SupportsIndex, SupportsAbs, and others. +* Special types: NewType, NamedTuple, TypedDict. +* Deprecated wrapper submodules for re and io related types. +* Deprecated aliases for builtin types and collections.abc ABCs. + +Any name not present in __all__ is an implementation detail +that may be changed without notice. Use at your own risk! +""" + +from abc import abstractmethod, ABCMeta +import collections +from collections import defaultdict +import collections.abc +import copyreg +import contextlib +import functools +import operator +import re as stdlib_re # Avoid confusion with the re we export. +import sys +import types +import warnings +from types import WrapperDescriptorType, MethodWrapperType, MethodDescriptorType, GenericAlias + +from _typing import ( + _idfunc, + TypeVar, + ParamSpec, + TypeVarTuple, + ParamSpecArgs, + ParamSpecKwargs, + TypeAliasType, + Generic, +) + +# Please keep __all__ alphabetized within each category. +__all__ = [ + # Super-special typing primitives. + 'Annotated', + 'Any', + 'Callable', + 'ClassVar', + 'Concatenate', + 'Final', + 'ForwardRef', + 'Generic', + 'Literal', + 'Optional', + 'ParamSpec', + 'Protocol', + 'Tuple', + 'Type', + 'TypeVar', + 'TypeVarTuple', + 'Union', + + # ABCs (from collections.abc). + 'AbstractSet', # collections.abc.Set. + 'ByteString', + 'Container', + 'ContextManager', + 'Hashable', + 'ItemsView', + 'Iterable', + 'Iterator', + 'KeysView', + 'Mapping', + 'MappingView', + 'MutableMapping', + 'MutableSequence', + 'MutableSet', + 'Sequence', + 'Sized', + 'ValuesView', + 'Awaitable', + 'AsyncIterator', + 'AsyncIterable', + 'Coroutine', + 'Collection', + 'AsyncGenerator', + 'AsyncContextManager', + + # Structural checks, a.k.a. protocols. + 'Reversible', + 'SupportsAbs', + 'SupportsBytes', + 'SupportsComplex', + 'SupportsFloat', + 'SupportsIndex', + 'SupportsInt', + 'SupportsRound', + + # Concrete collection types. + 'ChainMap', + 'Counter', + 'Deque', + 'Dict', + 'DefaultDict', + 'List', + 'OrderedDict', + 'Set', + 'FrozenSet', + 'NamedTuple', # Not really a type. + 'TypedDict', # Not really a type. + 'Generator', + + # Other concrete types. + 'BinaryIO', + 'IO', + 'Match', + 'Pattern', + 'TextIO', + + # One-off things. + 'AnyStr', + 'assert_type', + 'assert_never', + 'cast', + 'clear_overloads', + 'dataclass_transform', + 'final', + 'get_args', + 'get_origin', + 'get_overloads', + 'get_type_hints', + 'is_typeddict', + 'LiteralString', + 'Never', + 'NewType', + 'no_type_check', + 'no_type_check_decorator', + 'NoReturn', + 'NotRequired', + 'overload', + 'override', + 'ParamSpecArgs', + 'ParamSpecKwargs', + 'Required', + 'reveal_type', + 'runtime_checkable', + 'Self', + 'Text', + 'TYPE_CHECKING', + 'TypeAlias', + 'TypeGuard', + 'TypeAliasType', + 'Unpack', +] + +# The pseudo-submodules 're' and 'io' are part of the public +# namespace, but excluded from __all__ because they might stomp on +# legitimate imports of those modules. + + +def _type_convert(arg, module=None, *, allow_special_forms=False): + """For converting None to type(None), and strings to ForwardRef.""" + if arg is None: + return type(None) + if isinstance(arg, str): + return ForwardRef(arg, module=module, is_class=allow_special_forms) + return arg + + +def _type_check(arg, msg, is_argument=True, module=None, *, allow_special_forms=False): + """Check that the argument is a type, and return it (internal helper). + + As a special case, accept None and return type(None) instead. Also wrap strings + into ForwardRef instances. Consider several corner cases, for example plain + special forms like Union are not valid, while Union[int, str] is OK, etc. + The msg argument is a human-readable error message, e.g.:: + + "Union[arg, ...]: arg should be a type." + + We append the repr() of the actual value (truncated to 100 chars). + """ + invalid_generic_forms = (Generic, Protocol) + if not allow_special_forms: + invalid_generic_forms += (ClassVar,) + if is_argument: + invalid_generic_forms += (Final,) + + arg = _type_convert(arg, module=module, allow_special_forms=allow_special_forms) + if (isinstance(arg, _GenericAlias) and + arg.__origin__ in invalid_generic_forms): + raise TypeError(f"{arg} is not valid as type argument") + if arg in (Any, LiteralString, NoReturn, Never, Self, TypeAlias): + return arg + if allow_special_forms and arg in (ClassVar, Final): + return arg + if isinstance(arg, _SpecialForm) or arg in (Generic, Protocol): + raise TypeError(f"Plain {arg} is not valid as type argument") + if type(arg) is tuple: + raise TypeError(f"{msg} Got {arg!r:.100}.") + return arg + + +def _is_param_expr(arg): + return arg is ... or isinstance(arg, + (tuple, list, ParamSpec, _ConcatenateGenericAlias)) + + +def _should_unflatten_callable_args(typ, args): + """Internal helper for munging collections.abc.Callable's __args__. + + The canonical representation for a Callable's __args__ flattens the + argument types, see https://github.com/python/cpython/issues/86361. + + For example:: + + >>> import collections.abc + >>> P = ParamSpec('P') + >>> collections.abc.Callable[[int, int], str].__args__ == (int, int, str) + True + >>> collections.abc.Callable[P, str].__args__ == (P, str) + True + + As a result, if we need to reconstruct the Callable from its __args__, + we need to unflatten it. + """ + return ( + typ.__origin__ is collections.abc.Callable + and not (len(args) == 2 and _is_param_expr(args[0])) + ) + + +def _type_repr(obj): + """Return the repr() of an object, special-casing types (internal helper). + + If obj is a type, we return a shorter version than the default + type.__repr__, based on the module and qualified name, which is + typically enough to uniquely identify a type. For everything + else, we fall back on repr(obj). + """ + # When changing this function, don't forget about + # `_collections_abc._type_repr`, which does the same thing + # and must be consistent with this one. + if isinstance(obj, type): + if obj.__module__ == 'builtins': + return obj.__qualname__ + return f'{obj.__module__}.{obj.__qualname__}' + if obj is ...: + return '...' + if isinstance(obj, types.FunctionType): + return obj.__name__ + if isinstance(obj, tuple): + # Special case for `repr` of types with `ParamSpec`: + return '[' + ', '.join(_type_repr(t) for t in obj) + ']' + return repr(obj) + + +def _collect_parameters(args): + """Collect all type variables and parameter specifications in args + in order of first appearance (lexicographic order). + + For example:: + + >>> P = ParamSpec('P') + >>> T = TypeVar('T') + >>> _collect_parameters((T, Callable[P, T])) + (~T, ~P) + """ + parameters = [] + for t in args: + if isinstance(t, type): + # We don't want __parameters__ descriptor of a bare Python class. + pass + elif isinstance(t, tuple): + # `t` might be a tuple, when `ParamSpec` is substituted with + # `[T, int]`, or `[int, *Ts]`, etc. + for x in t: + for collected in _collect_parameters([x]): + if collected not in parameters: + parameters.append(collected) + elif hasattr(t, '__typing_subst__'): + if t not in parameters: + parameters.append(t) + else: + for x in getattr(t, '__parameters__', ()): + if x not in parameters: + parameters.append(x) + return tuple(parameters) + + +def _check_generic(cls, parameters, elen): + """Check correct count for parameters of a generic cls (internal helper). + + This gives a nice error message in case of count mismatch. + """ + if not elen: + raise TypeError(f"{cls} is not a generic class") + alen = len(parameters) + if alen != elen: + raise TypeError(f"Too {'many' if alen > elen else 'few'} arguments for {cls};" + f" actual {alen}, expected {elen}") + +def _unpack_args(args): + newargs = [] + for arg in args: + subargs = getattr(arg, '__typing_unpacked_tuple_args__', None) + if subargs is not None and not (subargs and subargs[-1] is ...): + newargs.extend(subargs) + else: + newargs.append(arg) + return newargs + +def _deduplicate(params): + # Weed out strict duplicates, preserving the first of each occurrence. + all_params = set(params) + if len(all_params) < len(params): + new_params = [] + for t in params: + if t in all_params: + new_params.append(t) + all_params.remove(t) + params = new_params + assert not all_params, all_params + return params + + +def _remove_dups_flatten(parameters): + """Internal helper for Union creation and substitution. + + Flatten Unions among parameters, then remove duplicates. + """ + # Flatten out Union[Union[...], ...]. + params = [] + for p in parameters: + if isinstance(p, (_UnionGenericAlias, types.UnionType)): + params.extend(p.__args__) + else: + params.append(p) + + return tuple(_deduplicate(params)) + + +def _flatten_literal_params(parameters): + """Internal helper for Literal creation: flatten Literals among parameters.""" + params = [] + for p in parameters: + if isinstance(p, _LiteralGenericAlias): + params.extend(p.__args__) + else: + params.append(p) + return tuple(params) + + +_cleanups = [] +_caches = {} + + +def _tp_cache(func=None, /, *, typed=False): + """Internal wrapper caching __getitem__ of generic types. + + For non-hashable arguments, the original function is used as a fallback. + """ + def decorator(func): + # The callback 'inner' references the newly created lru_cache + # indirectly by performing a lookup in the global '_caches' dictionary. + # This breaks a reference that can be problematic when combined with + # C API extensions that leak references to types. See GH-98253. + + cache = functools.lru_cache(typed=typed)(func) + _caches[func] = cache + _cleanups.append(cache.cache_clear) + del cache + + @functools.wraps(func) + def inner(*args, **kwds): + try: + return _caches[func](*args, **kwds) + except TypeError: + pass # All real errors (not unhashable args) are raised below. + return func(*args, **kwds) + return inner + + if func is not None: + return decorator(func) + + return decorator + +def _eval_type(t, globalns, localns, recursive_guard=frozenset()): + """Evaluate all forward references in the given type t. + + For use of globalns and localns see the docstring for get_type_hints(). + recursive_guard is used to prevent infinite recursion with a recursive + ForwardRef. + """ + if isinstance(t, ForwardRef): + return t._evaluate(globalns, localns, recursive_guard) + if isinstance(t, (_GenericAlias, GenericAlias, types.UnionType)): + if isinstance(t, GenericAlias): + args = tuple( + ForwardRef(arg) if isinstance(arg, str) else arg + for arg in t.__args__ + ) + is_unpacked = t.__unpacked__ + if _should_unflatten_callable_args(t, args): + t = t.__origin__[(args[:-1], args[-1])] + else: + t = t.__origin__[args] + if is_unpacked: + t = Unpack[t] + ev_args = tuple(_eval_type(a, globalns, localns, recursive_guard) for a in t.__args__) + if ev_args == t.__args__: + return t + if isinstance(t, GenericAlias): + return GenericAlias(t.__origin__, ev_args) + if isinstance(t, types.UnionType): + return functools.reduce(operator.or_, ev_args) + else: + return t.copy_with(ev_args) + return t + + +class _Final: + """Mixin to prohibit subclassing.""" + + __slots__ = ('__weakref__',) + + def __init_subclass__(cls, /, *args, **kwds): + if '_root' not in kwds: + raise TypeError("Cannot subclass special typing classes") + + +class _NotIterable: + """Mixin to prevent iteration, without being compatible with Iterable. + + That is, we could do:: + + def __iter__(self): raise TypeError() + + But this would make users of this mixin duck type-compatible with + collections.abc.Iterable - isinstance(foo, Iterable) would be True. + + Luckily, we can instead prevent iteration by setting __iter__ to None, which + is treated specially. + """ + + __slots__ = () + __iter__ = None + + +# Internal indicator of special typing constructs. +# See __doc__ instance attribute for specific docs. +class _SpecialForm(_Final, _NotIterable, _root=True): + __slots__ = ('_name', '__doc__', '_getitem') + + def __init__(self, getitem): + self._getitem = getitem + self._name = getitem.__name__ + self.__doc__ = getitem.__doc__ + + def __getattr__(self, item): + if item in {'__name__', '__qualname__'}: + return self._name + + raise AttributeError(item) + + def __mro_entries__(self, bases): + raise TypeError(f"Cannot subclass {self!r}") + + def __repr__(self): + return 'typing.' + self._name + + def __reduce__(self): + return self._name + + def __call__(self, *args, **kwds): + raise TypeError(f"Cannot instantiate {self!r}") + + def __or__(self, other): + return Union[self, other] + + def __ror__(self, other): + return Union[other, self] + + def __instancecheck__(self, obj): + raise TypeError(f"{self} cannot be used with isinstance()") + + def __subclasscheck__(self, cls): + raise TypeError(f"{self} cannot be used with issubclass()") + + @_tp_cache + def __getitem__(self, parameters): + return self._getitem(self, parameters) + + +class _LiteralSpecialForm(_SpecialForm, _root=True): + def __getitem__(self, parameters): + if not isinstance(parameters, tuple): + parameters = (parameters,) + return self._getitem(self, *parameters) + + +class _AnyMeta(type): + def __instancecheck__(self, obj): + if self is Any: + raise TypeError("typing.Any cannot be used with isinstance()") + return super().__instancecheck__(obj) + + def __repr__(self): + if self is Any: + return "typing.Any" + return super().__repr__() # respect to subclasses + + +class Any(metaclass=_AnyMeta): + """Special type indicating an unconstrained type. + + - Any is compatible with every type. + - Any assumed to have all methods. + - All values assumed to be instances of Any. + + Note that all the above statements are true from the point of view of + static type checkers. At runtime, Any should not be used with instance + checks. + """ + + def __new__(cls, *args, **kwargs): + if cls is Any: + raise TypeError("Any cannot be instantiated") + return super().__new__(cls, *args, **kwargs) + + +@_SpecialForm +def NoReturn(self, parameters): + """Special type indicating functions that never return. + + Example:: + + from typing import NoReturn + + def stop() -> NoReturn: + raise Exception('no way') + + NoReturn can also be used as a bottom type, a type that + has no values. Starting in Python 3.11, the Never type should + be used for this concept instead. Type checkers should treat the two + equivalently. + """ + raise TypeError(f"{self} is not subscriptable") + +# This is semantically identical to NoReturn, but it is implemented +# separately so that type checkers can distinguish between the two +# if they want. +@_SpecialForm +def Never(self, parameters): + """The bottom type, a type that has no members. + + This can be used to define a function that should never be + called, or a function that never returns:: + + from typing import Never + + def never_call_me(arg: Never) -> None: + pass + + def int_or_str(arg: int | str) -> None: + never_call_me(arg) # type checker error + match arg: + case int(): + print("It's an int") + case str(): + print("It's a str") + case _: + never_call_me(arg) # OK, arg is of type Never + """ + raise TypeError(f"{self} is not subscriptable") + + +@_SpecialForm +def Self(self, parameters): + """Used to spell the type of "self" in classes. + + Example:: + + from typing import Self + + class Foo: + def return_self(self) -> Self: + ... + return self + + This is especially useful for: + - classmethods that are used as alternative constructors + - annotating an `__enter__` method which returns self + """ + raise TypeError(f"{self} is not subscriptable") + + +@_SpecialForm +def LiteralString(self, parameters): + """Represents an arbitrary literal string. + + Example:: + + from typing import LiteralString + + def run_query(sql: LiteralString) -> None: + ... + + def caller(arbitrary_string: str, literal_string: LiteralString) -> None: + run_query("SELECT * FROM students") # OK + run_query(literal_string) # OK + run_query("SELECT * FROM " + literal_string) # OK + run_query(arbitrary_string) # type checker error + run_query( # type checker error + f"SELECT * FROM students WHERE name = {arbitrary_string}" + ) + + Only string literals and other LiteralStrings are compatible + with LiteralString. This provides a tool to help prevent + security issues such as SQL injection. + """ + raise TypeError(f"{self} is not subscriptable") + + +@_SpecialForm +def ClassVar(self, parameters): + """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(). + """ + item = _type_check(parameters, f'{self} accepts only single type.') + return _GenericAlias(self, (item,)) + +@_SpecialForm +def Final(self, parameters): + """Special typing construct to indicate final names to type checkers. + + A final name cannot be re-assigned or overridden in a subclass. + + For example:: + + MAX_SIZE: Final = 9000 + MAX_SIZE += 1 # Error reported by type checker + + class Connection: + TIMEOUT: Final[int] = 10 + + class FastConnector(Connection): + TIMEOUT = 1 # Error reported by type checker + + There is no runtime checking of these properties. + """ + item = _type_check(parameters, f'{self} accepts only single type.') + return _GenericAlias(self, (item,)) + +@_SpecialForm +def Union(self, parameters): + """Union type; Union[X, Y] means either X or Y. + + On Python 3.10 and higher, the | operator + can also be used to denote unions; + X | Y means the same thing to the type checker as Union[X, Y]. + + To define a union, use e.g. Union[int, str]. Details: + - The arguments must be types and there must be at least one. + - None as an argument is a special case and is replaced by + type(None). + - Unions of unions are flattened, e.g.:: + + assert Union[Union[int, str], float] == Union[int, str, float] + + - Unions of a single argument vanish, e.g.:: + + assert Union[int] == int # The constructor actually returns int + + - Redundant arguments are skipped, e.g.:: + + assert Union[int, str, int] == Union[int, str] + + - When comparing unions, the argument order is ignored, e.g.:: + + assert Union[int, str] == Union[str, int] + + - You cannot subclass or instantiate a union. + - You can use Optional[X] as a shorthand for Union[X, None]. + """ + if parameters == (): + raise TypeError("Cannot take a Union of no types.") + if not isinstance(parameters, tuple): + parameters = (parameters,) + msg = "Union[arg, ...]: each arg must be a type." + parameters = tuple(_type_check(p, msg) for p in parameters) + parameters = _remove_dups_flatten(parameters) + if len(parameters) == 1: + return parameters[0] + if len(parameters) == 2 and type(None) in parameters: + return _UnionGenericAlias(self, parameters, name="Optional") + return _UnionGenericAlias(self, parameters) + +def _make_union(left, right): + """Used from the C implementation of TypeVar. + + TypeVar.__or__ calls this instead of returning types.UnionType + because we want to allow unions between TypeVars and strings + (forward references). + """ + return Union[left, right] + +@_SpecialForm +def Optional(self, parameters): + """Optional[X] is equivalent to Union[X, None].""" + arg = _type_check(parameters, f"{self} requires a single type.") + return Union[arg, type(None)] + +@_LiteralSpecialForm +@_tp_cache(typed=True) +def Literal(self, *parameters): + """Special typing form to define literal types (a.k.a. value types). + + This form can be used to indicate to type checkers that the corresponding + variable or function parameter has a value equivalent to the provided + literal (or one of several literals):: + + def validate_simple(data: Any) -> Literal[True]: # always returns True + ... + + MODE = Literal['r', 'rb', 'w', 'wb'] + def open_helper(file: str, mode: MODE) -> str: + ... + + open_helper('/some/path', 'r') # Passes type check + open_helper('/other/path', 'typo') # Error in type checker + + Literal[...] cannot be subclassed. At runtime, an arbitrary value + is allowed as type argument to Literal[...], but type checkers may + impose restrictions. + """ + # There is no '_type_check' call because arguments to Literal[...] are + # values, not types. + parameters = _flatten_literal_params(parameters) + + try: + parameters = tuple(p for p, _ in _deduplicate(list(_value_and_type_iter(parameters)))) + except TypeError: # unhashable parameters + pass + + return _LiteralGenericAlias(self, parameters) + + +@_SpecialForm +def TypeAlias(self, parameters): + """Special form for marking type aliases. + + Use TypeAlias to indicate that an assignment should + be recognized as a proper type alias definition by type + checkers. + + For example:: + + Predicate: TypeAlias = Callable[..., bool] + + It's invalid when used anywhere except as in the example above. + """ + raise TypeError(f"{self} is not subscriptable") + + +@_SpecialForm +def Concatenate(self, parameters): + """Special form for annotating higher-order functions. + + ``Concatenate`` can be used in conjunction with ``ParamSpec`` and + ``Callable`` to represent a higher-order function which adds, removes or + transforms the parameters of a callable. + + For example:: + + Callable[Concatenate[int, P], int] + + See PEP 612 for detailed information. + """ + if parameters == (): + raise TypeError("Cannot take a Concatenate of no types.") + if not isinstance(parameters, tuple): + parameters = (parameters,) + if not (parameters[-1] is ... or isinstance(parameters[-1], ParamSpec)): + raise TypeError("The last parameter to Concatenate should be a " + "ParamSpec variable or ellipsis.") + msg = "Concatenate[arg, ...]: each arg must be a type." + parameters = (*(_type_check(p, msg) for p in parameters[:-1]), parameters[-1]) + return _ConcatenateGenericAlias(self, parameters) + + +@_SpecialForm +def TypeGuard(self, parameters): + """Special typing construct for marking user-defined type guard functions. + + ``TypeGuard`` can be used to annotate the return type of a user-defined + type guard function. ``TypeGuard`` only accepts a single type argument. + At runtime, functions marked this way should return a boolean. + + ``TypeGuard`` aims to benefit *type narrowing* -- a technique used by static + type checkers to determine a more precise type of an expression within a + program's code flow. Usually type narrowing is done by analyzing + conditional code flow and applying the narrowing to a block of code. The + conditional expression here is sometimes referred to as a "type guard". + + Sometimes it would be convenient to use a user-defined boolean function + as a type guard. Such a function should use ``TypeGuard[...]`` as its + return type to alert static type checkers to this intention. + + Using ``-> TypeGuard`` tells the static type checker that for a given + function: + + 1. The return value is a boolean. + 2. If the return value is ``True``, the type of its argument + is the type inside ``TypeGuard``. + + For example:: + + def is_str(val: Union[str, float]): + # "isinstance" type guard + if isinstance(val, str): + # Type of ``val`` is narrowed to ``str`` + ... + else: + # Else, type of ``val`` is narrowed to ``float``. + ... + + Strict type narrowing is not enforced -- ``TypeB`` need not be a narrower + form of ``TypeA`` (it can even be a wider form) and this may lead to + type-unsafe results. The main reason is to allow for things like + narrowing ``List[object]`` to ``List[str]`` even though the latter is not + a subtype of the former, since ``List`` is invariant. The responsibility of + writing type-safe type guards is left to the user. + + ``TypeGuard`` also works with type variables. For more information, see + PEP 647 (User-Defined Type Guards). + """ + item = _type_check(parameters, f'{self} accepts only single type.') + return _GenericAlias(self, (item,)) + + +class ForwardRef(_Final, _root=True): + """Internal wrapper to hold a forward reference.""" + + __slots__ = ('__forward_arg__', '__forward_code__', + '__forward_evaluated__', '__forward_value__', + '__forward_is_argument__', '__forward_is_class__', + '__forward_module__') + + def __init__(self, arg, is_argument=True, module=None, *, is_class=False): + if not isinstance(arg, str): + raise TypeError(f"Forward reference must be a string -- got {arg!r}") + + # If we do `def f(*args: *Ts)`, then we'll have `arg = '*Ts'`. + # Unfortunately, this isn't a valid expression on its own, so we + # do the unpacking manually. + if arg[0] == '*': + arg_to_compile = f'({arg},)[0]' # E.g. (*Ts,)[0] or (*tuple[int, int],)[0] + else: + arg_to_compile = arg + try: + code = compile(arg_to_compile, '<string>', 'eval') + except SyntaxError: + raise SyntaxError(f"Forward reference must be an expression -- got {arg!r}") + + self.__forward_arg__ = arg + self.__forward_code__ = code + self.__forward_evaluated__ = False + self.__forward_value__ = None + self.__forward_is_argument__ = is_argument + self.__forward_is_class__ = is_class + self.__forward_module__ = module + + def _evaluate(self, globalns, localns, recursive_guard): + if self.__forward_arg__ in recursive_guard: + return self + if not self.__forward_evaluated__ or localns is not globalns: + if globalns is None and localns is None: + globalns = localns = {} + elif globalns is None: + globalns = localns + elif localns is None: + localns = globalns + if self.__forward_module__ is not None: + globalns = getattr( + sys.modules.get(self.__forward_module__, None), '__dict__', globalns + ) + type_ = _type_check( + eval(self.__forward_code__, globalns, localns), + "Forward references must evaluate to types.", + is_argument=self.__forward_is_argument__, + allow_special_forms=self.__forward_is_class__, + ) + self.__forward_value__ = _eval_type( + type_, globalns, localns, recursive_guard | {self.__forward_arg__} + ) + self.__forward_evaluated__ = True + return self.__forward_value__ + + def __eq__(self, other): + if not isinstance(other, ForwardRef): + return NotImplemented + if self.__forward_evaluated__ and other.__forward_evaluated__: + return (self.__forward_arg__ == other.__forward_arg__ and + self.__forward_value__ == other.__forward_value__) + return (self.__forward_arg__ == other.__forward_arg__ and + self.__forward_module__ == other.__forward_module__) + + def __hash__(self): + return hash((self.__forward_arg__, self.__forward_module__)) + + def __or__(self, other): + return Union[self, other] + + def __ror__(self, other): + return Union[other, self] + + def __repr__(self): + if self.__forward_module__ is None: + module_repr = '' + else: + module_repr = f', module={self.__forward_module__!r}' + return f'ForwardRef({self.__forward_arg__!r}{module_repr})' + + +def _is_unpacked_typevartuple(x: Any) -> bool: + return ((not isinstance(x, type)) and + getattr(x, '__typing_is_unpacked_typevartuple__', False)) + + +def _is_typevar_like(x: Any) -> bool: + return isinstance(x, (TypeVar, ParamSpec)) or _is_unpacked_typevartuple(x) + + +class _PickleUsingNameMixin: + """Mixin enabling pickling based on self.__name__.""" + + def __reduce__(self): + return self.__name__ + + +def _typevar_subst(self, arg): + msg = "Parameters to generic types must be types." + arg = _type_check(arg, msg, is_argument=True) + if ((isinstance(arg, _GenericAlias) and arg.__origin__ is Unpack) or + (isinstance(arg, GenericAlias) and getattr(arg, '__unpacked__', False))): + raise TypeError(f"{arg} is not valid as type argument") + return arg + + +def _typevartuple_prepare_subst(self, alias, args): + params = alias.__parameters__ + typevartuple_index = params.index(self) + for param in params[typevartuple_index + 1:]: + if isinstance(param, TypeVarTuple): + raise TypeError(f"More than one TypeVarTuple parameter in {alias}") + + alen = len(args) + plen = len(params) + left = typevartuple_index + right = plen - typevartuple_index - 1 + var_tuple_index = None + fillarg = None + for k, arg in enumerate(args): + if not isinstance(arg, type): + subargs = getattr(arg, '__typing_unpacked_tuple_args__', None) + if subargs and len(subargs) == 2 and subargs[-1] is ...: + if var_tuple_index is not None: + raise TypeError("More than one unpacked arbitrary-length tuple argument") + var_tuple_index = k + fillarg = subargs[0] + if var_tuple_index is not None: + left = min(left, var_tuple_index) + right = min(right, alen - var_tuple_index - 1) + elif left + right > alen: + raise TypeError(f"Too few arguments for {alias};" + f" actual {alen}, expected at least {plen-1}") + + return ( + *args[:left], + *([fillarg]*(typevartuple_index - left)), + tuple(args[left: alen - right]), + *([fillarg]*(plen - right - left - typevartuple_index - 1)), + *args[alen - right:], + ) + + +def _paramspec_subst(self, arg): + if isinstance(arg, (list, tuple)): + arg = tuple(_type_check(a, "Expected a type.") for a in arg) + elif not _is_param_expr(arg): + raise TypeError(f"Expected a list of types, an ellipsis, " + f"ParamSpec, or Concatenate. Got {arg}") + return arg + + +def _paramspec_prepare_subst(self, alias, args): + params = alias.__parameters__ + i = params.index(self) + if i >= len(args): + raise TypeError(f"Too few arguments for {alias}") + # Special case where Z[[int, str, bool]] == Z[int, str, bool] in PEP 612. + if len(params) == 1 and not _is_param_expr(args[0]): + assert i == 0 + args = (args,) + # Convert lists to tuples to help other libraries cache the results. + elif isinstance(args[i], list): + args = (*args[:i], tuple(args[i]), *args[i+1:]) + return args + + +@_tp_cache +def _generic_class_getitem(cls, params): + """Parameterizes a generic class. + + At least, parameterizing a generic class is the *main* thing this method + does. For example, for some generic class `Foo`, this is called when we + do `Foo[int]` - there, with `cls=Foo` and `params=int`. + + However, note that this method is also called when defining generic + classes in the first place with `class Foo(Generic[T]): ...`. + """ + if not isinstance(params, tuple): + params = (params,) + + params = tuple(_type_convert(p) for p in params) + is_generic_or_protocol = cls in (Generic, Protocol) + + if is_generic_or_protocol: + # Generic and Protocol can only be subscripted with unique type variables. + if not params: + raise TypeError( + f"Parameter list to {cls.__qualname__}[...] cannot be empty" + ) + if not all(_is_typevar_like(p) for p in params): + raise TypeError( + f"Parameters to {cls.__name__}[...] must all be type variables " + f"or parameter specification variables.") + if len(set(params)) != len(params): + raise TypeError( + f"Parameters to {cls.__name__}[...] must all be unique") + else: + # Subscripting a regular Generic subclass. + for param in cls.__parameters__: + prepare = getattr(param, '__typing_prepare_subst__', None) + if prepare is not None: + params = prepare(cls, params) + _check_generic(cls, params, len(cls.__parameters__)) + + new_args = [] + for param, new_arg in zip(cls.__parameters__, params): + if isinstance(param, TypeVarTuple): + new_args.extend(new_arg) + else: + new_args.append(new_arg) + params = tuple(new_args) + + return _GenericAlias(cls, params) + + +def _generic_init_subclass(cls, *args, **kwargs): + super(Generic, cls).__init_subclass__(*args, **kwargs) + tvars = [] + if '__orig_bases__' in cls.__dict__: + error = Generic in cls.__orig_bases__ + else: + error = (Generic in cls.__bases__ and + cls.__name__ != 'Protocol' and + type(cls) != _TypedDictMeta) + if error: + raise TypeError("Cannot inherit from plain Generic") + if '__orig_bases__' in cls.__dict__: + tvars = _collect_parameters(cls.__orig_bases__) + # Look for Generic[T1, ..., Tn]. + # If found, tvars must be a subset of it. + # If not found, tvars is it. + # Also check for and reject plain Generic, + # and reject multiple Generic[...]. + gvars = None + for base in cls.__orig_bases__: + if (isinstance(base, _GenericAlias) and + base.__origin__ is Generic): + if gvars is not None: + raise TypeError( + "Cannot inherit from Generic[...] multiple times.") + gvars = base.__parameters__ + if gvars is not None: + tvarset = set(tvars) + gvarset = set(gvars) + if not tvarset <= gvarset: + s_vars = ', '.join(str(t) for t in tvars if t not in gvarset) + s_args = ', '.join(str(g) for g in gvars) + raise TypeError(f"Some type variables ({s_vars}) are" + f" not listed in Generic[{s_args}]") + tvars = gvars + cls.__parameters__ = tuple(tvars) + + +def _is_dunder(attr): + return attr.startswith('__') and attr.endswith('__') + +class _BaseGenericAlias(_Final, _root=True): + """The central part of the internal API. + + This represents a generic version of type 'origin' with type arguments 'params'. + There are two kind of these aliases: user defined and special. The special ones + are wrappers around builtin collections and ABCs in collections.abc. These must + have 'name' always set. If 'inst' is False, then the alias can't be instantiated; + this is used by e.g. typing.List and typing.Dict. + """ + + def __init__(self, origin, *, inst=True, name=None): + self._inst = inst + self._name = name + self.__origin__ = origin + self.__slots__ = None # This is not documented. + + def __call__(self, *args, **kwargs): + if not self._inst: + raise TypeError(f"Type {self._name} cannot be instantiated; " + f"use {self.__origin__.__name__}() instead") + result = self.__origin__(*args, **kwargs) + try: + result.__orig_class__ = self + except AttributeError: + pass + return result + + def __mro_entries__(self, bases): + res = [] + if self.__origin__ not in bases: + res.append(self.__origin__) + i = bases.index(self) + for b in bases[i+1:]: + if isinstance(b, _BaseGenericAlias) or issubclass(b, Generic): + break + else: + res.append(Generic) + return tuple(res) + + def __getattr__(self, attr): + if attr in {'__name__', '__qualname__'}: + return self._name or self.__origin__.__name__ + + # We are careful for copy and pickle. + # Also for simplicity we don't relay any dunder names + if '__origin__' in self.__dict__ and not _is_dunder(attr): + return getattr(self.__origin__, attr) + raise AttributeError(attr) + + def __setattr__(self, attr, val): + if _is_dunder(attr) or attr in {'_name', '_inst', '_nparams'}: + super().__setattr__(attr, val) + else: + setattr(self.__origin__, attr, val) + + def __instancecheck__(self, obj): + return self.__subclasscheck__(type(obj)) + + def __subclasscheck__(self, cls): + raise TypeError("Subscripted generics cannot be used with" + " class and instance checks") + + def __dir__(self): + return list(set(super().__dir__() + + [attr for attr in dir(self.__origin__) if not _is_dunder(attr)])) + + +# Special typing constructs Union, Optional, Generic, Callable and Tuple +# use three special attributes for internal bookkeeping of generic types: +# * __parameters__ is a tuple of unique free type parameters of a generic +# type, for example, Dict[T, T].__parameters__ == (T,); +# * __origin__ keeps a reference to a type that was subscripted, +# e.g., Union[T, int].__origin__ == Union, or the non-generic version of +# the type. +# * __args__ is a tuple of all arguments used in subscripting, +# e.g., Dict[T, int].__args__ == (T, int). + + +class _GenericAlias(_BaseGenericAlias, _root=True): + # The type of parameterized generics. + # + # That is, for example, `type(List[int])` is `_GenericAlias`. + # + # Objects which are instances of this class include: + # * Parameterized container types, e.g. `Tuple[int]`, `List[int]`. + # * Note that native container types, e.g. `tuple`, `list`, use + # `types.GenericAlias` instead. + # * Parameterized classes: + # class C[T]: pass + # # C[int] is a _GenericAlias + # * `Callable` aliases, generic `Callable` aliases, and + # parameterized `Callable` aliases: + # T = TypeVar('T') + # # _CallableGenericAlias inherits from _GenericAlias. + # A = Callable[[], None] # _CallableGenericAlias + # B = Callable[[T], None] # _CallableGenericAlias + # C = B[int] # _CallableGenericAlias + # * Parameterized `Final`, `ClassVar` and `TypeGuard`: + # # All _GenericAlias + # Final[int] + # ClassVar[float] + # TypeVar[bool] + + def __init__(self, origin, args, *, inst=True, name=None): + super().__init__(origin, inst=inst, name=name) + if not isinstance(args, tuple): + args = (args,) + self.__args__ = tuple(... if a is _TypingEllipsis else + a for a in args) + self.__parameters__ = _collect_parameters(args) + if not name: + self.__module__ = origin.__module__ + + def __eq__(self, other): + if not isinstance(other, _GenericAlias): + return NotImplemented + return (self.__origin__ == other.__origin__ + and self.__args__ == other.__args__) + + def __hash__(self): + return hash((self.__origin__, self.__args__)) + + def __or__(self, right): + return Union[self, right] + + def __ror__(self, left): + return Union[left, self] + + @_tp_cache + def __getitem__(self, args): + # Parameterizes an already-parameterized object. + # + # For example, we arrive here doing something like: + # T1 = TypeVar('T1') + # T2 = TypeVar('T2') + # T3 = TypeVar('T3') + # class A(Generic[T1]): pass + # B = A[T2] # B is a _GenericAlias + # C = B[T3] # Invokes _GenericAlias.__getitem__ + # + # We also arrive here when parameterizing a generic `Callable` alias: + # T = TypeVar('T') + # C = Callable[[T], None] + # C[int] # Invokes _GenericAlias.__getitem__ + + if self.__origin__ in (Generic, Protocol): + # Can't subscript Generic[...] or Protocol[...]. + raise TypeError(f"Cannot subscript already-subscripted {self}") + if not self.__parameters__: + raise TypeError(f"{self} is not a generic class") + + # Preprocess `args`. + if not isinstance(args, tuple): + args = (args,) + args = tuple(_type_convert(p) for p in args) + args = _unpack_args(args) + new_args = self._determine_new_args(args) + r = self.copy_with(new_args) + return r + + def _determine_new_args(self, args): + # Determines new __args__ for __getitem__. + # + # For example, suppose we had: + # T1 = TypeVar('T1') + # T2 = TypeVar('T2') + # class A(Generic[T1, T2]): pass + # T3 = TypeVar('T3') + # B = A[int, T3] + # C = B[str] + # `B.__args__` is `(int, T3)`, so `C.__args__` should be `(int, str)`. + # Unfortunately, this is harder than it looks, because if `T3` is + # anything more exotic than a plain `TypeVar`, we need to consider + # edge cases. + + params = self.__parameters__ + # In the example above, this would be {T3: str} + for param in params: + prepare = getattr(param, '__typing_prepare_subst__', None) + if prepare is not None: + args = prepare(self, args) + alen = len(args) + plen = len(params) + if alen != plen: + raise TypeError(f"Too {'many' if alen > plen else 'few'} arguments for {self};" + f" actual {alen}, expected {plen}") + new_arg_by_param = dict(zip(params, args)) + return tuple(self._make_substitution(self.__args__, new_arg_by_param)) + + def _make_substitution(self, args, new_arg_by_param): + """Create a list of new type arguments.""" + new_args = [] + for old_arg in args: + if isinstance(old_arg, type): + new_args.append(old_arg) + continue + + substfunc = getattr(old_arg, '__typing_subst__', None) + if substfunc: + new_arg = substfunc(new_arg_by_param[old_arg]) + else: + subparams = getattr(old_arg, '__parameters__', ()) + if not subparams: + new_arg = old_arg + else: + subargs = [] + for x in subparams: + if isinstance(x, TypeVarTuple): + subargs.extend(new_arg_by_param[x]) + else: + subargs.append(new_arg_by_param[x]) + new_arg = old_arg[tuple(subargs)] + + if self.__origin__ == collections.abc.Callable and isinstance(new_arg, tuple): + # Consider the following `Callable`. + # C = Callable[[int], str] + # Here, `C.__args__` should be (int, str) - NOT ([int], str). + # That means that if we had something like... + # P = ParamSpec('P') + # T = TypeVar('T') + # C = Callable[P, T] + # D = C[[int, str], float] + # ...we need to be careful; `new_args` should end up as + # `(int, str, float)` rather than `([int, str], float)`. + new_args.extend(new_arg) + elif _is_unpacked_typevartuple(old_arg): + # Consider the following `_GenericAlias`, `B`: + # class A(Generic[*Ts]): ... + # B = A[T, *Ts] + # If we then do: + # B[float, int, str] + # The `new_arg` corresponding to `T` will be `float`, and the + # `new_arg` corresponding to `*Ts` will be `(int, str)`. We + # should join all these types together in a flat list + # `(float, int, str)` - so again, we should `extend`. + new_args.extend(new_arg) + elif isinstance(old_arg, tuple): + # Corner case: + # P = ParamSpec('P') + # T = TypeVar('T') + # class Base(Generic[P]): ... + # Can be substituted like this: + # X = Base[[int, T]] + # In this case, `old_arg` will be a tuple: + new_args.append( + tuple(self._make_substitution(old_arg, new_arg_by_param)), + ) + else: + new_args.append(new_arg) + return new_args + + def copy_with(self, args): + return self.__class__(self.__origin__, args, name=self._name, inst=self._inst) + + def __repr__(self): + if self._name: + name = 'typing.' + self._name + else: + name = _type_repr(self.__origin__) + if self.__args__: + args = ", ".join([_type_repr(a) for a in self.__args__]) + else: + # To ensure the repr is eval-able. + args = "()" + return f'{name}[{args}]' + + def __reduce__(self): + if self._name: + origin = globals()[self._name] + else: + origin = self.__origin__ + args = tuple(self.__args__) + if len(args) == 1 and not isinstance(args[0], tuple): + args, = args + return operator.getitem, (origin, args) + + def __mro_entries__(self, bases): + if isinstance(self.__origin__, _SpecialForm): + raise TypeError(f"Cannot subclass {self!r}") + + if self._name: # generic version of an ABC or built-in class + return super().__mro_entries__(bases) + if self.__origin__ is Generic: + if Protocol in bases: + return () + i = bases.index(self) + for b in bases[i+1:]: + if isinstance(b, _BaseGenericAlias) and b is not self: + return () + return (self.__origin__,) + + def __iter__(self): + yield Unpack[self] + + +# _nparams is the number of accepted parameters, e.g. 0 for Hashable, +# 1 for List and 2 for Dict. It may be -1 if variable number of +# parameters are accepted (needs custom __getitem__). + +class _SpecialGenericAlias(_NotIterable, _BaseGenericAlias, _root=True): + def __init__(self, origin, nparams, *, inst=True, name=None): + if name is None: + name = origin.__name__ + super().__init__(origin, inst=inst, name=name) + self._nparams = nparams + if origin.__module__ == 'builtins': + self.__doc__ = f'A generic version of {origin.__qualname__}.' + else: + self.__doc__ = f'A generic version of {origin.__module__}.{origin.__qualname__}.' + + @_tp_cache + def __getitem__(self, params): + if not isinstance(params, tuple): + params = (params,) + msg = "Parameters to generic types must be types." + params = tuple(_type_check(p, msg) for p in params) + _check_generic(self, params, self._nparams) + return self.copy_with(params) + + def copy_with(self, params): + return _GenericAlias(self.__origin__, params, + name=self._name, inst=self._inst) + + def __repr__(self): + return 'typing.' + self._name + + def __subclasscheck__(self, cls): + if isinstance(cls, _SpecialGenericAlias): + return issubclass(cls.__origin__, self.__origin__) + if not isinstance(cls, _GenericAlias): + return issubclass(cls, self.__origin__) + return super().__subclasscheck__(cls) + + def __reduce__(self): + return self._name + + def __or__(self, right): + return Union[self, right] + + def __ror__(self, left): + return Union[left, self] + + +class _DeprecatedGenericAlias(_SpecialGenericAlias, _root=True): + def __init__( + self, origin, nparams, *, removal_version, inst=True, name=None + ): + super().__init__(origin, nparams, inst=inst, name=name) + self._removal_version = removal_version + + def __instancecheck__(self, inst): + import warnings + warnings._deprecated( + f"{self.__module__}.{self._name}", remove=self._removal_version + ) + return super().__instancecheck__(inst) + + +class _CallableGenericAlias(_NotIterable, _GenericAlias, _root=True): + def __repr__(self): + assert self._name == 'Callable' + args = self.__args__ + if len(args) == 2 and _is_param_expr(args[0]): + return super().__repr__() + return (f'typing.Callable' + f'[[{", ".join([_type_repr(a) for a in args[:-1]])}], ' + f'{_type_repr(args[-1])}]') + + def __reduce__(self): + args = self.__args__ + if not (len(args) == 2 and _is_param_expr(args[0])): + args = list(args[:-1]), args[-1] + return operator.getitem, (Callable, args) + + +class _CallableType(_SpecialGenericAlias, _root=True): + def copy_with(self, params): + return _CallableGenericAlias(self.__origin__, params, + name=self._name, inst=self._inst) + + def __getitem__(self, params): + if not isinstance(params, tuple) or len(params) != 2: + raise TypeError("Callable must be used as " + "Callable[[arg, ...], result].") + args, result = params + # This relaxes what args can be on purpose to allow things like + # PEP 612 ParamSpec. Responsibility for whether a user is using + # Callable[...] properly is deferred to static type checkers. + if isinstance(args, list): + params = (tuple(args), result) + else: + params = (args, result) + return self.__getitem_inner__(params) + + @_tp_cache + def __getitem_inner__(self, params): + args, result = params + msg = "Callable[args, result]: result must be a type." + result = _type_check(result, msg) + if args is Ellipsis: + return self.copy_with((_TypingEllipsis, result)) + if not isinstance(args, tuple): + args = (args,) + args = tuple(_type_convert(arg) for arg in args) + params = args + (result,) + return self.copy_with(params) + + +class _TupleType(_SpecialGenericAlias, _root=True): + @_tp_cache + def __getitem__(self, params): + if not isinstance(params, tuple): + params = (params,) + if len(params) >= 2 and params[-1] is ...: + msg = "Tuple[t, ...]: t must be a type." + params = tuple(_type_check(p, msg) for p in params[:-1]) + return self.copy_with((*params, _TypingEllipsis)) + msg = "Tuple[t0, t1, ...]: each t must be a type." + params = tuple(_type_check(p, msg) for p in params) + return self.copy_with(params) + + +class _UnionGenericAlias(_NotIterable, _GenericAlias, _root=True): + def copy_with(self, params): + return Union[params] + + def __eq__(self, other): + if not isinstance(other, (_UnionGenericAlias, types.UnionType)): + return NotImplemented + return set(self.__args__) == set(other.__args__) + + def __hash__(self): + return hash(frozenset(self.__args__)) + + def __repr__(self): + args = self.__args__ + if len(args) == 2: + if args[0] is type(None): + return f'typing.Optional[{_type_repr(args[1])}]' + elif args[1] is type(None): + return f'typing.Optional[{_type_repr(args[0])}]' + return super().__repr__() + + def __instancecheck__(self, obj): + return self.__subclasscheck__(type(obj)) + + def __subclasscheck__(self, cls): + for arg in self.__args__: + if issubclass(cls, arg): + return True + + def __reduce__(self): + func, (origin, args) = super().__reduce__() + return func, (Union, args) + + +def _value_and_type_iter(parameters): + return ((p, type(p)) for p in parameters) + + +class _LiteralGenericAlias(_GenericAlias, _root=True): + def __eq__(self, other): + if not isinstance(other, _LiteralGenericAlias): + return NotImplemented + + return set(_value_and_type_iter(self.__args__)) == set(_value_and_type_iter(other.__args__)) + + def __hash__(self): + return hash(frozenset(_value_and_type_iter(self.__args__))) + + +class _ConcatenateGenericAlias(_GenericAlias, _root=True): + def copy_with(self, params): + if isinstance(params[-1], (list, tuple)): + return (*params[:-1], *params[-1]) + if isinstance(params[-1], _ConcatenateGenericAlias): + params = (*params[:-1], *params[-1].__args__) + return super().copy_with(params) + + +@_SpecialForm +def Unpack(self, parameters): + """Type unpack operator. + + The type unpack operator takes the child types from some container type, + such as `tuple[int, str]` or a `TypeVarTuple`, and 'pulls them out'. + + For example:: + + # For some generic class `Foo`: + Foo[Unpack[tuple[int, str]]] # Equivalent to Foo[int, str] + + Ts = TypeVarTuple('Ts') + # Specifies that `Bar` is generic in an arbitrary number of types. + # (Think of `Ts` as a tuple of an arbitrary number of individual + # `TypeVar`s, which the `Unpack` is 'pulling out' directly into the + # `Generic[]`.) + class Bar(Generic[Unpack[Ts]]): ... + Bar[int] # Valid + Bar[int, str] # Also valid + + From Python 3.11, this can also be done using the `*` operator:: + + Foo[*tuple[int, str]] + class Bar(Generic[*Ts]): ... + + And from Python 3.12, it can be done using built-in syntax for generics:: + + Foo[*tuple[int, str]] + class Bar[*Ts]: ... + + The operator can also be used along with a `TypedDict` to annotate + `**kwargs` in a function signature:: + + class Movie(TypedDict): + name: str + year: int + + # This function expects two keyword arguments - *name* of type `str` and + # *year* of type `int`. + def foo(**kwargs: Unpack[Movie]): ... + + Note that there is only some runtime checking of this operator. Not + everything the runtime allows may be accepted by static type checkers. + + For more information, see PEPs 646 and 692. + """ + item = _type_check(parameters, f'{self} accepts only single type.') + return _UnpackGenericAlias(origin=self, args=(item,)) + + +class _UnpackGenericAlias(_GenericAlias, _root=True): + def __repr__(self): + # `Unpack` only takes one argument, so __args__ should contain only + # a single item. + return f'typing.Unpack[{_type_repr(self.__args__[0])}]' + + def __getitem__(self, args): + if self.__typing_is_unpacked_typevartuple__: + return args + return super().__getitem__(args) + + @property + def __typing_unpacked_tuple_args__(self): + assert self.__origin__ is Unpack + assert len(self.__args__) == 1 + arg, = self.__args__ + if isinstance(arg, _GenericAlias): + assert arg.__origin__ is tuple + return arg.__args__ + return None + + @property + def __typing_is_unpacked_typevartuple__(self): + assert self.__origin__ is Unpack + assert len(self.__args__) == 1 + return isinstance(self.__args__[0], TypeVarTuple) + + +class _TypingEllipsis: + """Internal placeholder for ... (ellipsis).""" + + +_TYPING_INTERNALS = frozenset({ + '__parameters__', '__orig_bases__', '__orig_class__', + '_is_protocol', '_is_runtime_protocol', '__protocol_attrs__', + '__non_callable_proto_members__', '__type_params__', +}) + +_SPECIAL_NAMES = frozenset({ + '__abstractmethods__', '__annotations__', '__dict__', '__doc__', + '__init__', '__module__', '__new__', '__slots__', + '__subclasshook__', '__weakref__', '__class_getitem__' +}) + +# These special attributes will be not collected as protocol members. +EXCLUDED_ATTRIBUTES = _TYPING_INTERNALS | _SPECIAL_NAMES | {'_MutableMapping__marker'} + + +def _get_protocol_attrs(cls): + """Collect protocol members from a protocol class objects. + + This includes names actually defined in the class dictionary, as well + as names that appear in annotations. Special names (above) are skipped. + """ + attrs = set() + for base in cls.__mro__[:-1]: # without object + if base.__name__ in {'Protocol', 'Generic'}: + continue + annotations = getattr(base, '__annotations__', {}) + for attr in (*base.__dict__, *annotations): + if not attr.startswith('_abc_') and attr not in EXCLUDED_ATTRIBUTES: + attrs.add(attr) + return attrs + + +def _no_init_or_replace_init(self, *args, **kwargs): + cls = type(self) + + if cls._is_protocol: + raise TypeError('Protocols cannot be instantiated') + + # Already using a custom `__init__`. No need to calculate correct + # `__init__` to call. This can lead to RecursionError. See bpo-45121. + if cls.__init__ is not _no_init_or_replace_init: + return + + # Initially, `__init__` of a protocol subclass is set to `_no_init_or_replace_init`. + # The first instantiation of the subclass will call `_no_init_or_replace_init` which + # searches for a proper new `__init__` in the MRO. The new `__init__` + # replaces the subclass' old `__init__` (ie `_no_init_or_replace_init`). Subsequent + # instantiation of the protocol subclass will thus use the new + # `__init__` and no longer call `_no_init_or_replace_init`. + for base in cls.__mro__: + init = base.__dict__.get('__init__', _no_init_or_replace_init) + if init is not _no_init_or_replace_init: + cls.__init__ = init + break + else: + # should not happen + cls.__init__ = object.__init__ + + cls.__init__(self, *args, **kwargs) + + +def _caller(depth=1, default='__main__'): + try: + return sys._getframemodulename(depth + 1) or default + except AttributeError: # For platforms without _getframemodulename() + pass + try: + return sys._getframe(depth + 1).f_globals.get('__name__', default) + except (AttributeError, ValueError): # For platforms without _getframe() + pass + return None + +def _allow_reckless_class_checks(depth=2): + """Allow instance and class checks for special stdlib modules. + + The abc and functools modules indiscriminately call isinstance() and + issubclass() on the whole MRO of a user class, which may contain protocols. + """ + return _caller(depth) in {'abc', 'functools', None} + + +_PROTO_ALLOWLIST = { + 'collections.abc': [ + 'Callable', 'Awaitable', 'Iterable', 'Iterator', 'AsyncIterable', + 'Hashable', 'Sized', 'Container', 'Collection', 'Reversible', 'Buffer', + ], + 'contextlib': ['AbstractContextManager', 'AbstractAsyncContextManager'], +} + + +@functools.cache +def _lazy_load_getattr_static(): + # Import getattr_static lazily so as not to slow down the import of typing.py + # Cache the result so we don't slow down _ProtocolMeta.__instancecheck__ unnecessarily + from inspect import getattr_static + return getattr_static + + +_cleanups.append(_lazy_load_getattr_static.cache_clear) + +def _pickle_psargs(psargs): + return ParamSpecArgs, (psargs.__origin__,) + +copyreg.pickle(ParamSpecArgs, _pickle_psargs) + +def _pickle_pskwargs(pskwargs): + return ParamSpecKwargs, (pskwargs.__origin__,) + +copyreg.pickle(ParamSpecKwargs, _pickle_pskwargs) + +del _pickle_psargs, _pickle_pskwargs + + +class _ProtocolMeta(ABCMeta): + # This metaclass is somewhat unfortunate, + # but is necessary for several reasons... + def __new__(mcls, name, bases, namespace, /, **kwargs): + if name == "Protocol" and bases == (Generic,): + pass + elif Protocol in bases: + for base in bases: + if not ( + base in {object, Generic} + or base.__name__ in _PROTO_ALLOWLIST.get(base.__module__, []) + or ( + issubclass(base, Generic) + and getattr(base, "_is_protocol", False) + ) + ): + raise TypeError( + f"Protocols can only inherit from other protocols, " + f"got {base!r}" + ) + return super().__new__(mcls, name, bases, namespace, **kwargs) + + def __init__(cls, *args, **kwargs): + super().__init__(*args, **kwargs) + if getattr(cls, "_is_protocol", False): + cls.__protocol_attrs__ = _get_protocol_attrs(cls) + + def __subclasscheck__(cls, other): + if cls is Protocol: + return type.__subclasscheck__(cls, other) + if ( + getattr(cls, '_is_protocol', False) + and not _allow_reckless_class_checks() + ): + if not isinstance(other, type): + # Same error message as for issubclass(1, int). + raise TypeError('issubclass() arg 1 must be a class') + if not getattr(cls, '_is_runtime_protocol', False): + raise TypeError( + "Instance and class checks can only be used with " + "@runtime_checkable protocols" + ) + if ( + # this attribute is set by @runtime_checkable: + cls.__non_callable_proto_members__ + and cls.__dict__.get("__subclasshook__") is _proto_hook + ): + raise TypeError( + "Protocols with non-method members don't support issubclass()" + ) + return super().__subclasscheck__(other) + + def __instancecheck__(cls, instance): + # We need this method for situations where attributes are + # assigned in __init__. + if cls is Protocol: + return type.__instancecheck__(cls, instance) + if not getattr(cls, "_is_protocol", False): + # i.e., it's a concrete subclass of a protocol + return super().__instancecheck__(instance) + + if ( + not getattr(cls, '_is_runtime_protocol', False) and + not _allow_reckless_class_checks() + ): + raise TypeError("Instance and class checks can only be used with" + " @runtime_checkable protocols") + + if super().__instancecheck__(instance): + return True + + getattr_static = _lazy_load_getattr_static() + for attr in cls.__protocol_attrs__: + try: + val = getattr_static(instance, attr) + except AttributeError: + break + # this attribute is set by @runtime_checkable: + if val is None and attr not in cls.__non_callable_proto_members__: + break + else: + return True + + return False + + +@classmethod +def _proto_hook(cls, other): + if not cls.__dict__.get('_is_protocol', False): + return NotImplemented + + for attr in cls.__protocol_attrs__: + for base in other.__mro__: + # Check if the members appears in the class dictionary... + if attr in base.__dict__: + if base.__dict__[attr] is None: + return NotImplemented + break + + # ...or in annotations, if it is a sub-protocol. + annotations = getattr(base, '__annotations__', {}) + if (isinstance(annotations, collections.abc.Mapping) and + attr in annotations and + issubclass(other, Generic) and getattr(other, '_is_protocol', False)): + break + else: + return NotImplemented + return True + + +class Protocol(Generic, metaclass=_ProtocolMeta): + """Base class for protocol classes. + + Protocol classes are defined as:: + + class Proto(Protocol): + def meth(self) -> int: + ... + + Such classes are primarily used with static type checkers that recognize + structural subtyping (static duck-typing). + + For example:: + + class C: + def meth(self) -> int: + return 0 + + def func(x: Proto) -> int: + return x.meth() + + func(C()) # Passes static type check + + See PEP 544 for details. Protocol classes decorated with + @typing.runtime_checkable act as simple-minded runtime protocols that check + only the presence of given attributes, ignoring their type signatures. + Protocol classes can be generic, they are defined as:: + + class GenProto[T](Protocol): + def meth(self) -> T: + ... + """ + + __slots__ = () + _is_protocol = True + _is_runtime_protocol = False + + def __init_subclass__(cls, *args, **kwargs): + super().__init_subclass__(*args, **kwargs) + + # Determine if this is a protocol or a concrete subclass. + if not cls.__dict__.get('_is_protocol', False): + cls._is_protocol = any(b is Protocol for b in cls.__bases__) + + # Set (or override) the protocol subclass hook. + if '__subclasshook__' not in cls.__dict__: + cls.__subclasshook__ = _proto_hook + + # Prohibit instantiation for protocol classes + if cls._is_protocol and cls.__init__ is Protocol.__init__: + cls.__init__ = _no_init_or_replace_init + + +class _AnnotatedAlias(_NotIterable, _GenericAlias, _root=True): + """Runtime representation of an annotated type. + + At its core 'Annotated[t, dec1, dec2, ...]' is an alias for the type 't' + with extra annotations. The alias behaves like a normal typing alias. + Instantiating is the same as instantiating the underlying type; binding + it to types is also the same. + + The metadata itself is stored in a '__metadata__' attribute as a tuple. + """ + + def __init__(self, origin, metadata): + if isinstance(origin, _AnnotatedAlias): + metadata = origin.__metadata__ + metadata + origin = origin.__origin__ + super().__init__(origin, origin, name='Annotated') + self.__metadata__ = metadata + + def copy_with(self, params): + assert len(params) == 1 + new_type = params[0] + return _AnnotatedAlias(new_type, self.__metadata__) + + def __repr__(self): + return "typing.Annotated[{}, {}]".format( + _type_repr(self.__origin__), + ", ".join(repr(a) for a in self.__metadata__) + ) + + def __reduce__(self): + return operator.getitem, ( + Annotated, (self.__origin__,) + self.__metadata__ + ) + + def __eq__(self, other): + if not isinstance(other, _AnnotatedAlias): + return NotImplemented + return (self.__origin__ == other.__origin__ + and self.__metadata__ == other.__metadata__) + + def __hash__(self): + return hash((self.__origin__, self.__metadata__)) + + def __getattr__(self, attr): + if attr in {'__name__', '__qualname__'}: + return 'Annotated' + return super().__getattr__(attr) + + def __mro_entries__(self, bases): + return (self.__origin__,) + + +class Annotated: + """Add context-specific metadata to a type. + + Example: Annotated[int, runtime_check.Unsigned] indicates to the + hypothetical runtime_check module that this type is an unsigned int. + Every other consumer of this type can ignore this metadata and treat + this type as int. + + The first argument to Annotated must be a valid type. + + Details: + + - It's an error to call `Annotated` with less than two arguments. + - Access the metadata via the ``__metadata__`` attribute:: + + assert Annotated[int, '$'].__metadata__ == ('$',) + + - Nested Annotated types are flattened:: + + assert Annotated[Annotated[T, Ann1, Ann2], Ann3] == Annotated[T, Ann1, Ann2, Ann3] + + - Instantiating an annotated type is equivalent to instantiating the + underlying type:: + + assert Annotated[C, Ann1](5) == C(5) + + - Annotated can be used as a generic type alias:: + + type Optimized[T] = Annotated[T, runtime.Optimize()] + # type checker will treat Optimized[int] + # as equivalent to Annotated[int, runtime.Optimize()] + + type OptimizedList[T] = Annotated[list[T], runtime.Optimize()] + # type checker will treat OptimizedList[int] + # as equivalent to Annotated[list[int], runtime.Optimize()] + + - Annotated cannot be used with an unpacked TypeVarTuple:: + + type Variadic[*Ts] = Annotated[*Ts, Ann1] # NOT valid + + This would be equivalent to:: + + Annotated[T1, T2, T3, ..., Ann1] + + where T1, T2 etc. are TypeVars, which would be invalid, because + only one type should be passed to Annotated. + """ + + __slots__ = () + + def __new__(cls, *args, **kwargs): + raise TypeError("Type Annotated cannot be instantiated.") + + def __class_getitem__(cls, params): + if not isinstance(params, tuple): + params = (params,) + return cls._class_getitem_inner(cls, *params) + + @_tp_cache(typed=True) + def _class_getitem_inner(cls, *params): + if len(params) < 2: + raise TypeError("Annotated[...] should be used " + "with at least two arguments (a type and an " + "annotation).") + if _is_unpacked_typevartuple(params[0]): + raise TypeError("Annotated[...] should not be used with an " + "unpacked TypeVarTuple") + msg = "Annotated[t, ...]: t must be a type." + origin = _type_check(params[0], msg, allow_special_forms=True) + metadata = tuple(params[1:]) + return _AnnotatedAlias(origin, metadata) + + def __init_subclass__(cls, *args, **kwargs): + raise TypeError( + "Cannot subclass {}.Annotated".format(cls.__module__) + ) + + +def runtime_checkable(cls): + """Mark a protocol class as a runtime protocol. + + Such protocol can be used with isinstance() and issubclass(). + Raise TypeError if applied to a non-protocol class. + This allows a simple-minded structural check very similar to + one trick ponies in collections.abc such as Iterable. + + For example:: + + @runtime_checkable + class Closable(Protocol): + def close(self): ... + + assert isinstance(open('/some/file'), Closable) + + Warning: this will check only the presence of the required methods, + not their type signatures! + """ + if not issubclass(cls, Generic) or not getattr(cls, '_is_protocol', False): + raise TypeError('@runtime_checkable can be only applied to protocol classes,' + ' got %r' % cls) + cls._is_runtime_protocol = True + # PEP 544 prohibits using issubclass() + # with protocols that have non-method members. + # See gh-113320 for why we compute this attribute here, + # rather than in `_ProtocolMeta.__init__` + cls.__non_callable_proto_members__ = set() + for attr in cls.__protocol_attrs__: + try: + is_callable = callable(getattr(cls, attr, None)) + except Exception as e: + raise TypeError( + f"Failed to determine whether protocol member {attr!r} " + "is a method member" + ) from e + else: + if not is_callable: + cls.__non_callable_proto_members__.add(attr) + return cls + + +def cast(typ, val): + """Cast a value to a type. + + This returns the value unchanged. To the type checker this + signals that the return value has the designated type, but at + runtime we intentionally don't check anything (we want this + to be as fast as possible). + """ + return val + + +def assert_type(val, typ, /): + """Ask a static type checker to confirm that the value is of the given type. + + At runtime this does nothing: it returns the first argument unchanged with no + checks or side effects, no matter the actual type of the argument. + + When a static type checker encounters a call to assert_type(), it + emits an error if the value is not of the specified type:: + + def greet(name: str) -> None: + assert_type(name, str) # OK + assert_type(name, int) # type checker error + """ + return val + + +_allowed_types = (types.FunctionType, types.BuiltinFunctionType, + types.MethodType, types.ModuleType, + WrapperDescriptorType, MethodWrapperType, MethodDescriptorType) + + +def get_type_hints(obj, globalns=None, localns=None, include_extras=False): + """Return type hints for an object. + + This is often the same as obj.__annotations__, but it handles + forward references encoded as string literals and recursively replaces all + 'Annotated[T, ...]' with 'T' (unless 'include_extras=True'). + + The argument may be a module, class, method, or function. The annotations + are returned as a dictionary. For classes, annotations include also + inherited members. + + 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. + + - If no dict arguments are passed, an attempt is made to use the + globals from obj (or the respective module's globals for classes), + and these are also used as the locals. If the object does not appear + to have globals, an empty dictionary is used. For classes, the search + order is globals first then locals. + + - If one dict argument is passed, it is used for both globals and + locals. + + - If two dict arguments are passed, they specify globals and + locals, respectively. + """ + if getattr(obj, '__no_type_check__', None): + return {} + # Classes require a special treatment. + if isinstance(obj, type): + hints = {} + for base in reversed(obj.__mro__): + if globalns is None: + base_globals = getattr(sys.modules.get(base.__module__, None), '__dict__', {}) + else: + base_globals = globalns + ann = base.__dict__.get('__annotations__', {}) + if isinstance(ann, types.GetSetDescriptorType): + ann = {} + base_locals = dict(vars(base)) if localns is None else localns + if localns is None and globalns is None: + # This is surprising, but required. Before Python 3.10, + # get_type_hints only evaluated the globalns of + # a class. To maintain backwards compatibility, we reverse + # the globalns and localns order so that eval() looks into + # *base_globals* first rather than *base_locals*. + # This only affects ForwardRefs. + base_globals, base_locals = base_locals, base_globals + for name, value in ann.items(): + if value is None: + value = type(None) + if isinstance(value, str): + value = ForwardRef(value, is_argument=False, is_class=True) + value = _eval_type(value, base_globals, base_locals) + hints[name] = value + return hints if include_extras else {k: _strip_annotations(t) for k, t in hints.items()} + + if globalns is None: + if isinstance(obj, types.ModuleType): + globalns = obj.__dict__ + else: + nsobj = obj + # Find globalns for the unwrapped object. + while hasattr(nsobj, '__wrapped__'): + nsobj = nsobj.__wrapped__ + globalns = getattr(nsobj, '__globals__', {}) + if localns is None: + localns = globalns + elif localns is None: + localns = globalns + hints = getattr(obj, '__annotations__', None) + if hints is None: + # Return empty annotations for something that _could_ have them. + if isinstance(obj, _allowed_types): + return {} + else: + raise TypeError('{!r} is not a module, class, method, ' + 'or function.'.format(obj)) + hints = dict(hints) + for name, value in hints.items(): + if value is None: + value = type(None) + if isinstance(value, str): + # class-level forward refs were handled above, this must be either + # a module-level annotation or a function argument annotation + value = ForwardRef( + value, + is_argument=not isinstance(obj, types.ModuleType), + is_class=False, + ) + hints[name] = _eval_type(value, globalns, localns) + return hints if include_extras else {k: _strip_annotations(t) for k, t in hints.items()} + + +def _strip_annotations(t): + """Strip the annotations from a given type.""" + if isinstance(t, _AnnotatedAlias): + return _strip_annotations(t.__origin__) + if hasattr(t, "__origin__") and t.__origin__ in (Required, NotRequired): + return _strip_annotations(t.__args__[0]) + if isinstance(t, _GenericAlias): + stripped_args = tuple(_strip_annotations(a) for a in t.__args__) + if stripped_args == t.__args__: + return t + return t.copy_with(stripped_args) + if isinstance(t, GenericAlias): + stripped_args = tuple(_strip_annotations(a) for a in t.__args__) + if stripped_args == t.__args__: + return t + return GenericAlias(t.__origin__, stripped_args) + if isinstance(t, types.UnionType): + stripped_args = tuple(_strip_annotations(a) for a in t.__args__) + if stripped_args == t.__args__: + return t + return functools.reduce(operator.or_, stripped_args) + + return t + + +def get_origin(tp): + """Get the unsubscripted version of a type. + + This supports generic types, Callable, Tuple, Union, Literal, Final, ClassVar, + Annotated, and others. Return None for unsupported types. + + Examples:: + + >>> P = ParamSpec('P') + >>> assert get_origin(Literal[42]) is Literal + >>> assert get_origin(int) is None + >>> assert get_origin(ClassVar[int]) is ClassVar + >>> assert get_origin(Generic) is Generic + >>> assert get_origin(Generic[T]) is Generic + >>> assert get_origin(Union[T, int]) is Union + >>> assert get_origin(List[Tuple[T, T]][int]) is list + >>> assert get_origin(P.args) is P + """ + if isinstance(tp, _AnnotatedAlias): + return Annotated + if isinstance(tp, (_BaseGenericAlias, GenericAlias, + ParamSpecArgs, ParamSpecKwargs)): + return tp.__origin__ + if tp is Generic: + return Generic + if isinstance(tp, types.UnionType): + return types.UnionType + return None + + +def get_args(tp): + """Get type arguments with all substitutions performed. + + For unions, basic simplifications used by Union constructor are performed. + + Examples:: + + >>> T = TypeVar('T') + >>> assert get_args(Dict[str, int]) == (str, int) + >>> assert get_args(int) == () + >>> assert get_args(Union[int, Union[T, int], str][int]) == (int, str) + >>> assert get_args(Union[int, Tuple[T, int]][str]) == (int, Tuple[str, int]) + >>> assert get_args(Callable[[], T][int]) == ([], int) + """ + if isinstance(tp, _AnnotatedAlias): + return (tp.__origin__,) + tp.__metadata__ + if isinstance(tp, (_GenericAlias, GenericAlias)): + res = tp.__args__ + if _should_unflatten_callable_args(tp, res): + res = (list(res[:-1]), res[-1]) + return res + if isinstance(tp, types.UnionType): + return tp.__args__ + return () + + +def is_typeddict(tp): + """Check if an annotation is a TypedDict class. + + For example:: + + >>> from typing import TypedDict + >>> class Film(TypedDict): + ... title: str + ... year: int + ... + >>> is_typeddict(Film) + True + >>> is_typeddict(dict) + False + """ + return isinstance(tp, _TypedDictMeta) + + +_ASSERT_NEVER_REPR_MAX_LENGTH = 100 + + +def assert_never(arg: Never, /) -> Never: + """Statically assert that a line of code is unreachable. + + Example:: + + def int_or_str(arg: int | str) -> None: + match arg: + case int(): + print("It's an int") + case str(): + print("It's a str") + case _: + assert_never(arg) + + If a type checker finds that a call to assert_never() is + reachable, it will emit an error. + + At runtime, this throws an exception when called. + """ + value = repr(arg) + if len(value) > _ASSERT_NEVER_REPR_MAX_LENGTH: + value = value[:_ASSERT_NEVER_REPR_MAX_LENGTH] + '...' + raise AssertionError(f"Expected code to be unreachable, but got: {value}") + + +def no_type_check(arg): + """Decorator to indicate that annotations are not type hints. + + The argument must be a class or function; if it is a class, it + applies recursively to all methods and classes defined in that class + (but not to methods defined in its superclasses or subclasses). + + This mutates the function(s) or class(es) in place. + """ + if isinstance(arg, type): + for key in dir(arg): + obj = getattr(arg, key) + if ( + not hasattr(obj, '__qualname__') + or obj.__qualname__ != f'{arg.__qualname__}.{obj.__name__}' + or getattr(obj, '__module__', None) != arg.__module__ + ): + # We only modify objects that are defined in this type directly. + # If classes / methods are nested in multiple layers, + # we will modify them when processing their direct holders. + continue + # Instance, class, and static methods: + if isinstance(obj, types.FunctionType): + obj.__no_type_check__ = True + if isinstance(obj, types.MethodType): + obj.__func__.__no_type_check__ = True + # Nested types: + if isinstance(obj, type): + no_type_check(obj) + try: + arg.__no_type_check__ = True + except TypeError: # built-in classes + pass + return arg + + +def no_type_check_decorator(decorator): + """Decorator to give another decorator the @no_type_check effect. + + This wraps the decorator with something that wraps the decorated + function in @no_type_check. + """ + @functools.wraps(decorator) + def wrapped_decorator(*args, **kwds): + func = decorator(*args, **kwds) + func = no_type_check(func) + return func + + return wrapped_decorator + + +def _overload_dummy(*args, **kwds): + """Helper for @overload to raise when called.""" + raise NotImplementedError( + "You should not call an overloaded function. " + "A series of @overload-decorated functions " + "outside a stub module should always be followed " + "by an implementation that is not @overload-ed.") + + +# {module: {qualname: {firstlineno: func}}} +_overload_registry = defaultdict(functools.partial(defaultdict, dict)) + + +def overload(func): + """Decorator for overloaded functions/methods. + + In a stub file, place two or more stub definitions for the same + function in a row, each decorated with @overload. + + For example:: + + @overload + def utf8(value: None) -> None: ... + @overload + def utf8(value: bytes) -> bytes: ... + @overload + def utf8(value: str) -> bytes: ... + + In a non-stub file (i.e. a regular .py file), do the same but + follow it with an implementation. The implementation should *not* + be decorated with @overload:: + + @overload + def utf8(value: None) -> None: ... + @overload + def utf8(value: bytes) -> bytes: ... + @overload + def utf8(value: str) -> bytes: ... + def utf8(value): + ... # implementation goes here + + The overloads for a function can be retrieved at runtime using the + get_overloads() function. + """ + # classmethod and staticmethod + f = getattr(func, "__func__", func) + try: + _overload_registry[f.__module__][f.__qualname__][f.__code__.co_firstlineno] = func + except AttributeError: + # Not a normal function; ignore. + pass + return _overload_dummy + + +def get_overloads(func): + """Return all defined overloads for *func* as a sequence.""" + # classmethod and staticmethod + f = getattr(func, "__func__", func) + if f.__module__ not in _overload_registry: + return [] + mod_dict = _overload_registry[f.__module__] + if f.__qualname__ not in mod_dict: + return [] + return list(mod_dict[f.__qualname__].values()) + + +def clear_overloads(): + """Clear all overloads in the registry.""" + _overload_registry.clear() + + +def final(f): + """Decorator to indicate final methods and final classes. + + Use this decorator to indicate to type checkers that the decorated + method cannot be overridden, and decorated class cannot be subclassed. + + For example:: + + class Base: + @final + def done(self) -> None: + ... + class Sub(Base): + def done(self) -> None: # Error reported by type checker + ... + + @final + class Leaf: + ... + class Other(Leaf): # Error reported by type checker + ... + + There is no runtime checking of these properties. The decorator + attempts to set the ``__final__`` attribute to ``True`` on the decorated + object to allow runtime introspection. + """ + try: + f.__final__ = True + except (AttributeError, TypeError): + # Skip the attribute silently if it is not writable. + # AttributeError happens if the object has __slots__ or a + # read-only property, TypeError if it's a builtin class. + pass + return f + + +# Some unconstrained type variables. These were initially used by the container types. +# They were never meant for export and are now unused, but we keep them around to +# avoid breaking compatibility with users who import them. +T = TypeVar('T') # Any type. +KT = TypeVar('KT') # Key type. +VT = TypeVar('VT') # Value type. +T_co = TypeVar('T_co', covariant=True) # Any type covariant containers. +V_co = TypeVar('V_co', covariant=True) # Any type covariant containers. +VT_co = TypeVar('VT_co', covariant=True) # Value type covariant containers. +T_contra = TypeVar('T_contra', contravariant=True) # Ditto contravariant. +# Internal type variable used for Type[]. +CT_co = TypeVar('CT_co', covariant=True, bound=type) + + +# A useful type variable with constraints. This represents string types. +# (This one *is* for export!) +AnyStr = TypeVar('AnyStr', bytes, str) + + +# Various ABCs mimicking those in collections.abc. +_alias = _SpecialGenericAlias + +Hashable = _alias(collections.abc.Hashable, 0) # Not generic. +Awaitable = _alias(collections.abc.Awaitable, 1) +Coroutine = _alias(collections.abc.Coroutine, 3) +AsyncIterable = _alias(collections.abc.AsyncIterable, 1) +AsyncIterator = _alias(collections.abc.AsyncIterator, 1) +Iterable = _alias(collections.abc.Iterable, 1) +Iterator = _alias(collections.abc.Iterator, 1) +Reversible = _alias(collections.abc.Reversible, 1) +Sized = _alias(collections.abc.Sized, 0) # Not generic. +Container = _alias(collections.abc.Container, 1) +Collection = _alias(collections.abc.Collection, 1) +Callable = _CallableType(collections.abc.Callable, 2) +Callable.__doc__ = \ + """Deprecated alias to collections.abc.Callable. + + Callable[[int], str] signifies a function that takes a single + parameter of type int and returns a str. + + The subscription syntax must always be used with exactly two + values: the argument list and the return type. + The argument list must be a list of types, a ParamSpec, + Concatenate or ellipsis. The return type must be a single type. + + There is no syntax to indicate optional or keyword arguments; + such function types are rarely used as callback types. + """ +AbstractSet = _alias(collections.abc.Set, 1, name='AbstractSet') +MutableSet = _alias(collections.abc.MutableSet, 1) +# NOTE: Mapping is only covariant in the value type. +Mapping = _alias(collections.abc.Mapping, 2) +MutableMapping = _alias(collections.abc.MutableMapping, 2) +Sequence = _alias(collections.abc.Sequence, 1) +MutableSequence = _alias(collections.abc.MutableSequence, 1) +ByteString = _DeprecatedGenericAlias( + collections.abc.ByteString, 0, removal_version=(3, 14) # Not generic. +) +# Tuple accepts variable number of parameters. +Tuple = _TupleType(tuple, -1, inst=False, name='Tuple') +Tuple.__doc__ = \ + """Deprecated alias to builtins.tuple. + + Tuple[X, Y] is the cross-product type of X and Y. + + Example: Tuple[T1, T2] is a tuple of two elements corresponding + to type variables T1 and T2. Tuple[int, float, str] is a tuple + of an int, a float and a string. + + To specify a variable-length tuple of homogeneous type, use Tuple[T, ...]. + """ +List = _alias(list, 1, inst=False, name='List') +Deque = _alias(collections.deque, 1, name='Deque') +Set = _alias(set, 1, inst=False, name='Set') +FrozenSet = _alias(frozenset, 1, inst=False, name='FrozenSet') +MappingView = _alias(collections.abc.MappingView, 1) +KeysView = _alias(collections.abc.KeysView, 1) +ItemsView = _alias(collections.abc.ItemsView, 2) +ValuesView = _alias(collections.abc.ValuesView, 1) +ContextManager = _alias(contextlib.AbstractContextManager, 1, name='ContextManager') +AsyncContextManager = _alias(contextlib.AbstractAsyncContextManager, 1, name='AsyncContextManager') +Dict = _alias(dict, 2, inst=False, name='Dict') +DefaultDict = _alias(collections.defaultdict, 2, name='DefaultDict') +OrderedDict = _alias(collections.OrderedDict, 2) +Counter = _alias(collections.Counter, 1) +ChainMap = _alias(collections.ChainMap, 2) +Generator = _alias(collections.abc.Generator, 3) +AsyncGenerator = _alias(collections.abc.AsyncGenerator, 2) +Type = _alias(type, 1, inst=False, name='Type') +Type.__doc__ = \ + """Deprecated alias to builtins.type. + + builtins.type or typing.Type can be used to annotate class objects. + For example, suppose we have the following classes:: + + class User: ... # Abstract base for User classes + class BasicUser(User): ... + class ProUser(User): ... + class TeamUser(User): ... + + And a function that takes a class argument that's a subclass of + User and returns an instance of the corresponding class:: + + def new_user[U](user_class: Type[U]) -> U: + user = user_class() + # (Here we could write the user object to a database) + return user + + joe = new_user(BasicUser) + + At this point the type checker knows that joe has type BasicUser. + """ + + +@runtime_checkable +class SupportsInt(Protocol): + """An ABC with one abstract method __int__.""" + + __slots__ = () + + @abstractmethod + def __int__(self) -> int: + pass + + +@runtime_checkable +class SupportsFloat(Protocol): + """An ABC with one abstract method __float__.""" + + __slots__ = () + + @abstractmethod + def __float__(self) -> float: + pass + + +@runtime_checkable +class SupportsComplex(Protocol): + """An ABC with one abstract method __complex__.""" + + __slots__ = () + + @abstractmethod + def __complex__(self) -> complex: + pass + + +@runtime_checkable +class SupportsBytes(Protocol): + """An ABC with one abstract method __bytes__.""" + + __slots__ = () + + @abstractmethod + def __bytes__(self) -> bytes: + pass + + +@runtime_checkable +class SupportsIndex(Protocol): + """An ABC with one abstract method __index__.""" + + __slots__ = () + + @abstractmethod + def __index__(self) -> int: + pass + + +@runtime_checkable +class SupportsAbs[T](Protocol): + """An ABC with one abstract method __abs__ that is covariant in its return type.""" + + __slots__ = () + + @abstractmethod + def __abs__(self) -> T: + pass + + +@runtime_checkable +class SupportsRound[T](Protocol): + """An ABC with one abstract method __round__ that is covariant in its return type.""" + + __slots__ = () + + @abstractmethod + def __round__(self, ndigits: int = 0) -> T: + pass + + +def _make_nmtuple(name, types, module, defaults = ()): + fields = [n for n, t in types] + types = {n: _type_check(t, f"field {n} annotation must be a type") + for n, t in types} + nm_tpl = collections.namedtuple(name, fields, + defaults=defaults, module=module) + nm_tpl.__annotations__ = nm_tpl.__new__.__annotations__ = types + return nm_tpl + + +# attributes prohibited to set in NamedTuple class syntax +_prohibited = frozenset({'__new__', '__init__', '__slots__', '__getnewargs__', + '_fields', '_field_defaults', + '_make', '_replace', '_asdict', '_source'}) + +_special = frozenset({'__module__', '__name__', '__annotations__'}) + + +class NamedTupleMeta(type): + def __new__(cls, typename, bases, ns): + assert _NamedTuple in bases + for base in bases: + if base is not _NamedTuple and base is not Generic: + raise TypeError( + 'can only inherit from a NamedTuple type and Generic') + bases = tuple(tuple if base is _NamedTuple else base for base in bases) + types = ns.get('__annotations__', {}) + default_names = [] + for field_name in types: + if field_name in ns: + default_names.append(field_name) + elif default_names: + raise TypeError(f"Non-default namedtuple field {field_name} " + f"cannot follow default field" + f"{'s' if len(default_names) > 1 else ''} " + f"{', '.join(default_names)}") + nm_tpl = _make_nmtuple(typename, types.items(), + defaults=[ns[n] for n in default_names], + module=ns['__module__']) + nm_tpl.__bases__ = bases + if Generic in bases: + class_getitem = _generic_class_getitem + nm_tpl.__class_getitem__ = classmethod(class_getitem) + # update from user namespace without overriding special namedtuple attributes + for key in ns: + if key in _prohibited: + raise AttributeError("Cannot overwrite NamedTuple attribute " + key) + elif key not in _special and key not in nm_tpl._fields: + setattr(nm_tpl, key, ns[key]) + if Generic in bases: + nm_tpl.__init_subclass__() + return nm_tpl + + +def NamedTuple(typename, fields=None, /, **kwargs): + """Typed version of namedtuple. + + Usage:: + + class Employee(NamedTuple): + name: str + id: int + + This is equivalent to:: + + Employee = collections.namedtuple('Employee', ['name', 'id']) + + The resulting class has an extra __annotations__ attribute, giving a + dict that maps field names to types. (The field names are also in + the _fields attribute, which is part of the namedtuple API.) + An alternative equivalent functional syntax is also accepted:: + + Employee = NamedTuple('Employee', [('name', str), ('id', int)]) + """ + if fields is None: + fields = kwargs.items() + elif kwargs: + raise TypeError("Either list of fields or keywords" + " can be provided to NamedTuple, not both") + nt = _make_nmtuple(typename, fields, module=_caller()) + nt.__orig_bases__ = (NamedTuple,) + return nt + +_NamedTuple = type.__new__(NamedTupleMeta, 'NamedTuple', (), {}) + +def _namedtuple_mro_entries(bases): + assert NamedTuple in bases + return (_NamedTuple,) + +NamedTuple.__mro_entries__ = _namedtuple_mro_entries + + +class _TypedDictMeta(type): + def __new__(cls, name, bases, ns, total=True): + """Create a new typed dict class object. + + This method is called when TypedDict is subclassed, + or when TypedDict is instantiated. This way + TypedDict supports all three syntax forms described in its docstring. + Subclasses and instances of TypedDict return actual dictionaries. + """ + for base in bases: + if type(base) is not _TypedDictMeta and base is not Generic: + raise TypeError('cannot inherit from both a TypedDict type ' + 'and a non-TypedDict base class') + + if any(issubclass(b, Generic) for b in bases): + generic_base = (Generic,) + else: + generic_base = () + + tp_dict = type.__new__(_TypedDictMeta, name, (*generic_base, dict), ns) + + if not hasattr(tp_dict, '__orig_bases__'): + tp_dict.__orig_bases__ = bases + + annotations = {} + own_annotations = ns.get('__annotations__', {}) + msg = "TypedDict('Name', {f0: t0, f1: t1, ...}); each t must be a type" + own_annotations = { + n: _type_check(tp, msg, module=tp_dict.__module__) + for n, tp in own_annotations.items() + } + required_keys = set() + optional_keys = set() + + for base in bases: + annotations.update(base.__dict__.get('__annotations__', {})) + + base_required = base.__dict__.get('__required_keys__', set()) + required_keys |= base_required + optional_keys -= base_required + + base_optional = base.__dict__.get('__optional_keys__', set()) + required_keys -= base_optional + optional_keys |= base_optional + + annotations.update(own_annotations) + for annotation_key, annotation_type in own_annotations.items(): + annotation_origin = get_origin(annotation_type) + if annotation_origin is Annotated: + annotation_args = get_args(annotation_type) + if annotation_args: + annotation_type = annotation_args[0] + annotation_origin = get_origin(annotation_type) + + if annotation_origin is Required: + is_required = True + elif annotation_origin is NotRequired: + is_required = False + else: + is_required = total + + if is_required: + required_keys.add(annotation_key) + optional_keys.discard(annotation_key) + else: + optional_keys.add(annotation_key) + required_keys.discard(annotation_key) + + assert required_keys.isdisjoint(optional_keys), ( + f"Required keys overlap with optional keys in {name}:" + f" {required_keys=}, {optional_keys=}" + ) + tp_dict.__annotations__ = annotations + tp_dict.__required_keys__ = frozenset(required_keys) + tp_dict.__optional_keys__ = frozenset(optional_keys) + if not hasattr(tp_dict, '__total__'): + tp_dict.__total__ = total + return tp_dict + + __call__ = dict # static method + + def __subclasscheck__(cls, other): + # Typed dicts are only for static structural subtyping. + raise TypeError('TypedDict does not support instance and class checks') + + __instancecheck__ = __subclasscheck__ + + +def TypedDict(typename, fields=None, /, *, total=True, **kwargs): + """A simple typed namespace. At runtime it is equivalent to a plain dict. + + TypedDict creates a dictionary type such that a type checker will expect all + 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. + + 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 + >>> Point2D(x=1, y=2, label='first') == dict(x=1, y=2, label='first') + True + + The type info can be accessed via the Point2D.__annotations__ dict, and + the Point2D.__required_keys__ and Point2D.__optional_keys__ frozensets. + TypedDict supports an additional equivalent form:: + + Point2D = TypedDict('Point2D', {'x': int, 'y': int, 'label': str}) + + By default, all keys must be present in a TypedDict. It is possible + to override this by specifying totality:: + + class Point2D(TypedDict, total=False): + x: int + y: int + + This means that a Point2D TypedDict can have any of the keys omitted. A type + checker is only expected to support a literal False or True as the value of + the total argument. True is the default, and makes all items defined in the + class body be required. + + The Required and NotRequired special forms can also be used to mark + individual keys as being required or not required:: + + class Point2D(TypedDict): + x: int # the "x" key must always be present (Required is the default) + y: NotRequired[int] # the "y" key can be omitted + + See PEP 655 for more details on Required and NotRequired. + """ + if fields is None: + fields = kwargs + elif kwargs: + raise TypeError("TypedDict takes either a dict or keyword arguments," + " but not both") + if kwargs: + warnings.warn( + "The kwargs-based syntax for TypedDict definitions is deprecated " + "in Python 3.11, will be removed in Python 3.13, and may not be " + "understood by third-party type checkers.", + DeprecationWarning, + stacklevel=2, + ) + + ns = {'__annotations__': dict(fields)} + module = _caller() + if module is not None: + # Setting correct module is necessary to make typed dict classes pickleable. + ns['__module__'] = module + + td = _TypedDictMeta(typename, (), ns, total=total) + td.__orig_bases__ = (TypedDict,) + return td + +_TypedDict = type.__new__(_TypedDictMeta, 'TypedDict', (), {}) +TypedDict.__mro_entries__ = lambda bases: (_TypedDict,) + + +@_SpecialForm +def Required(self, parameters): + """Special typing construct to mark a TypedDict key as required. + + This is mainly useful for total=False TypedDicts. + + For example:: + + class Movie(TypedDict, total=False): + title: Required[str] + year: int + + m = Movie( + title='The Matrix', # typechecker error if key is omitted + year=1999, + ) + + There is no runtime checking that a required key is actually provided + when instantiating a related TypedDict. + """ + item = _type_check(parameters, f'{self._name} accepts only a single type.') + return _GenericAlias(self, (item,)) + + +@_SpecialForm +def NotRequired(self, parameters): + """Special typing construct to mark a TypedDict key as potentially missing. + + For example:: + + class Movie(TypedDict): + title: str + year: NotRequired[int] + + m = Movie( + title='The Matrix', # typechecker error if key is omitted + year=1999, + ) + """ + item = _type_check(parameters, f'{self._name} accepts only a single type.') + return _GenericAlias(self, (item,)) + + +class NewType: + """NewType creates simple unique types with almost zero runtime overhead. + + NewType(name, tp) is considered a subtype of tp + by static type checkers. At runtime, NewType(name, tp) returns + a dummy callable that simply returns its argument. + + Usage:: + + UserId = NewType('UserId', int) + + def name_by_id(user_id: UserId) -> str: + ... + + UserId('user') # Fails type check + + name_by_id(42) # Fails type check + name_by_id(UserId(42)) # OK + + num = UserId(5) + 1 # type: int + """ + + __call__ = _idfunc + + def __init__(self, name, tp): + self.__qualname__ = name + if '.' in name: + name = name.rpartition('.')[-1] + self.__name__ = name + self.__supertype__ = tp + def_mod = _caller() + if def_mod != 'typing': + self.__module__ = def_mod + + def __mro_entries__(self, bases): + # We defined __mro_entries__ to get a better error message + # if a user attempts to subclass a NewType instance. bpo-46170 + superclass_name = self.__name__ + + class Dummy: + def __init_subclass__(cls): + subclass_name = cls.__name__ + raise TypeError( + f"Cannot subclass an instance of NewType. Perhaps you were looking for: " + f"`{subclass_name} = NewType({subclass_name!r}, {superclass_name})`" + ) + + return (Dummy,) + + def __repr__(self): + return f'{self.__module__}.{self.__qualname__}' + + def __reduce__(self): + return self.__qualname__ + + def __or__(self, other): + return Union[self, other] + + def __ror__(self, other): + return Union[other, self] + + +# Python-version-specific alias (Python 2: unicode; Python 3: str) +Text = str + + +# Constant that's True when type checking, but False here. +TYPE_CHECKING = False + + +class IO(Generic[AnyStr]): + """Generic base class for TextIO and BinaryIO. + + This is an abstract, generic version of the return of open(). + + NOTE: This does not distinguish between the different possible + classes (text vs. binary, read vs. write vs. read/write, + append-only, unbuffered). The TextIO and BinaryIO subclasses + below capture the distinctions between text vs. binary, which is + pervasive in the interface; however we currently do not offer a + way to track the other distinctions in the type system. + """ + + __slots__ = () + + @property + @abstractmethod + def mode(self) -> str: + pass + + @property + @abstractmethod + def name(self) -> str: + pass + + @abstractmethod + def close(self) -> None: + pass + + @property + @abstractmethod + def closed(self) -> bool: + pass + + @abstractmethod + def fileno(self) -> int: + pass + + @abstractmethod + def flush(self) -> None: + pass + + @abstractmethod + def isatty(self) -> bool: + pass + + @abstractmethod + def read(self, n: int = -1) -> AnyStr: + pass + + @abstractmethod + def readable(self) -> bool: + pass + + @abstractmethod + def readline(self, limit: int = -1) -> AnyStr: + pass + + @abstractmethod + def readlines(self, hint: int = -1) -> List[AnyStr]: + pass + + @abstractmethod + def seek(self, offset: int, whence: int = 0) -> int: + pass + + @abstractmethod + def seekable(self) -> bool: + pass + + @abstractmethod + def tell(self) -> int: + pass + + @abstractmethod + def truncate(self, size: int = None) -> int: + pass + + @abstractmethod + def writable(self) -> bool: + pass + + @abstractmethod + def write(self, s: AnyStr) -> int: + pass + + @abstractmethod + def writelines(self, lines: List[AnyStr]) -> None: + pass + + @abstractmethod + def __enter__(self) -> 'IO[AnyStr]': + pass + + @abstractmethod + def __exit__(self, type, value, traceback) -> None: + pass + + +class BinaryIO(IO[bytes]): + """Typed version of the return of open() in binary mode.""" + + __slots__ = () + + @abstractmethod + def write(self, s: Union[bytes, bytearray]) -> int: + pass + + @abstractmethod + def __enter__(self) -> 'BinaryIO': + pass + + +class TextIO(IO[str]): + """Typed version of the return of open() in text mode.""" + + __slots__ = () + + @property + @abstractmethod + def buffer(self) -> BinaryIO: + pass + + @property + @abstractmethod + def encoding(self) -> str: + pass + + @property + @abstractmethod + def errors(self) -> Optional[str]: + pass + + @property + @abstractmethod + def line_buffering(self) -> bool: + pass + + @property + @abstractmethod + def newlines(self) -> Any: + pass + + @abstractmethod + def __enter__(self) -> 'TextIO': + pass + + +class _DeprecatedType(type): + def __getattribute__(cls, name): + if name not in ("__dict__", "__module__") and name in cls.__dict__: + warnings.warn( + f"{cls.__name__} is deprecated, import directly " + f"from typing instead. {cls.__name__} will be removed " + "in Python 3.12.", + DeprecationWarning, + stacklevel=2, + ) + return super().__getattribute__(name) + + +class io(metaclass=_DeprecatedType): + """Wrapper namespace for IO generic classes.""" + + __all__ = ['IO', 'TextIO', 'BinaryIO'] + IO = IO + TextIO = TextIO + BinaryIO = BinaryIO + + +io.__name__ = __name__ + '.io' +sys.modules[io.__name__] = io + +Pattern = _alias(stdlib_re.Pattern, 1) +Match = _alias(stdlib_re.Match, 1) + +class re(metaclass=_DeprecatedType): + """Wrapper namespace for re type aliases.""" + + __all__ = ['Pattern', 'Match'] + Pattern = Pattern + Match = Match + + +re.__name__ = __name__ + '.re' +sys.modules[re.__name__] = re + + +def reveal_type[T](obj: T, /) -> T: + """Ask a static type checker to reveal the inferred type of an expression. + + When a static type checker encounters a call to ``reveal_type()``, + it will emit the inferred type of the argument:: + + x: int = 1 + reveal_type(x) + + Running a static type checker (e.g., mypy) on this example + will produce output similar to 'Revealed type is "builtins.int"'. + + At runtime, the function prints the runtime type of the + argument and returns the argument unchanged. + """ + print(f"Runtime type is {type(obj).__name__!r}", file=sys.stderr) + return obj + + +class _IdentityCallable(Protocol): + def __call__[T](self, arg: T, /) -> T: + ... + + +def dataclass_transform( + *, + eq_default: bool = True, + order_default: bool = False, + kw_only_default: bool = False, + frozen_default: bool = False, + field_specifiers: tuple[type[Any] | Callable[..., Any], ...] = (), + **kwargs: Any, +) -> _IdentityCallable: + """Decorator to mark an object as providing dataclass-like behaviour. + + The decorator can be applied to a function, class, or metaclass. + + Example usage with a decorator function:: + + @dataclass_transform() + def create_model[T](cls: type[T]) -> type[T]: + ... + return cls + + @create_model + class CustomerModel: + id: int + name: str + + On a base class:: + + @dataclass_transform() + class ModelBase: ... + + class CustomerModel(ModelBase): + id: int + name: str + + On a metaclass:: + + @dataclass_transform() + class ModelMeta(type): ... + + class ModelBase(metaclass=ModelMeta): ... + + class CustomerModel(ModelBase): + id: int + name: str + + The ``CustomerModel`` classes defined above will + be treated by type checkers similarly to classes created with + ``@dataclasses.dataclass``. + For example, type checkers will assume these classes have + ``__init__`` methods that accept ``id`` and ``name``. + + The arguments to this decorator can be used to customize this behavior: + - ``eq_default`` indicates whether the ``eq`` parameter is assumed to be + ``True`` or ``False`` if it is omitted by the caller. + - ``order_default`` indicates whether the ``order`` parameter is + assumed to be True or False if it is omitted by the caller. + - ``kw_only_default`` indicates whether the ``kw_only`` parameter is + assumed to be True or False if it is omitted by the caller. + - ``frozen_default`` indicates whether the ``frozen`` parameter is + assumed to be True or False if it is omitted by the caller. + - ``field_specifiers`` specifies a static list of supported classes + or functions that describe fields, similar to ``dataclasses.field()``. + - Arbitrary other keyword arguments are accepted in order to allow for + possible future extensions. + + At runtime, this decorator records its arguments in the + ``__dataclass_transform__`` attribute on the decorated object. + It has no other runtime effect. + + See PEP 681 for more details. + """ + def decorator(cls_or_fn): + cls_or_fn.__dataclass_transform__ = { + "eq_default": eq_default, + "order_default": order_default, + "kw_only_default": kw_only_default, + "frozen_default": frozen_default, + "field_specifiers": field_specifiers, + "kwargs": kwargs, + } + return cls_or_fn + return decorator + + +type _Func = Callable[..., Any] + + +def override[F: _Func](method: F, /) -> F: + """Indicate that a method is intended to override a method in a base class. + + Usage:: + + class Base: + def method(self) -> None: + pass + + class Child(Base): + @override + def method(self) -> None: + super().method() + + When this decorator is applied to a method, the type checker will + validate that it overrides a method or attribute with the same name on a + base class. This helps prevent bugs that may occur when a base class is + changed without an equivalent change to a child class. + + There is no runtime checking of this property. The decorator attempts to + set the ``__override__`` attribute to ``True`` on the decorated object to + allow runtime introspection. + + See PEP 698 for details. + """ + try: + method.__override__ = True + except (AttributeError, TypeError): + # Skip the attribute silently if it is not writable. + # AttributeError happens if the object has __slots__ or a + # read-only property, TypeError if it's a builtin class. + pass + return method |