""" 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 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 annotationlib from annotationlib import ForwardRef import collections from collections import defaultdict import collections.abc import copyreg import functools import operator import sys import types from types import GenericAlias from _typing import ( _idfunc, TypeVar, ParamSpec, TypeVarTuple, ParamSpecArgs, ParamSpecKwargs, TypeAliasType, Generic, NoDefault, ) # 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. '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', 'evaluate_forward_ref', 'final', 'get_args', 'get_origin', 'get_overloads', 'get_protocol_members', 'get_type_hints', 'is_protocol', 'is_typeddict', 'LiteralString', 'Never', 'NewType', 'no_type_check', 'no_type_check_decorator', 'NoDefault', 'NoReturn', 'NotRequired', 'overload', 'override', 'ParamSpecArgs', 'ParamSpecKwargs', 'ReadOnly', 'Required', 'reveal_type', 'runtime_checkable', 'Self', 'Text', 'TYPE_CHECKING', 'TypeAlias', 'TypeGuard', 'TypeIs', 'TypeAliasType', 'Unpack', ] 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 _make_forward_ref(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). """ if isinstance(obj, tuple): # Special case for `repr` of types with `ParamSpec`: return '[' + ', '.join(_type_repr(t) for t in obj) + ']' return annotationlib.value_to_string(obj) def _collect_type_parameters(args, *, enforce_default_ordering: bool = True): """Collect all type parameters in args in order of first appearance (lexicographic order). For example:: >>> P = ParamSpec('P') >>> T = TypeVar('T') >>> _collect_type_parameters((T, Callable[P, T])) (~T, ~P) """ # required type parameter cannot appear after parameter with default default_encountered = False # or after TypeVarTuple type_var_tuple_encountered = False 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_type_parameters([x]): if collected not in parameters: parameters.append(collected) elif hasattr(t, '__typing_subst__'): if t not in parameters: if enforce_default_ordering: if type_var_tuple_encountered and t.has_default(): raise TypeError('Type parameter with a default' ' follows TypeVarTuple') if t.has_default(): default_encountered = True elif default_encountered: raise TypeError(f'Type parameter {t!r} without a default' ' follows type parameter with a default') parameters.append(t) else: if _is_unpacked_typevartuple(t): type_var_tuple_encountered = True for x in getattr(t, '__parameters__', ()): if x not in parameters: parameters.append(x) return tuple(parameters) def _check_generic_specialization(cls, arguments): """Check correct count for parameters of a generic cls (internal helper). This gives a nice error message in case of count mismatch. """ expected_len = len(cls.__parameters__) if not expected_len: raise TypeError(f"{cls} is not a generic class") actual_len = len(arguments) if actual_len != expected_len: # deal with defaults if actual_len < expected_len: # If the parameter at index `actual_len` in the parameters list # has a default, then all parameters after it must also have # one, because we validated as much in _collect_type_parameters(). # That means that no error needs to be raised here, despite # the number of arguments being passed not matching the number # of parameters: all parameters that aren't explicitly # specialized in this call are parameters with default values. if cls.__parameters__[actual_len].has_default(): return expected_len -= sum(p.has_default() for p in cls.__parameters__) expect_val = f"at least {expected_len}" else: expect_val = expected_len raise TypeError(f"Too {'many' if actual_len > expected_len else 'few'} arguments" f" for {cls}; actual {actual_len}, expected {expect_val}") 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, *, unhashable_fallback=False): # Weed out strict duplicates, preserving the first of each occurrence. try: return dict.fromkeys(params) except TypeError: if not unhashable_fallback: raise # Happens for cases like `Annotated[dict, {'x': IntValidator()}]` return _deduplicate_unhashable(params) def _deduplicate_unhashable(unhashable_params): new_unhashable = [] for t in unhashable_params: if t not in new_unhashable: new_unhashable.append(t) return new_unhashable def _compare_args_orderless(first_args, second_args): first_unhashable = _deduplicate_unhashable(first_args) second_unhashable = _deduplicate_unhashable(second_args) t = list(second_unhashable) try: for elem in first_unhashable: t.remove(elem) except ValueError: return False return not t 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, unhashable_fallback=True)) 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 _deprecation_warning_for_no_type_params_passed(funcname: str) -> None: import warnings depr_message = ( f"Failing to pass a value to the 'type_params' parameter " f"of {funcname!r} is deprecated, as it leads to incorrect behaviour " f"when calling {funcname} on a stringified annotation " f"that references a PEP 695 type parameter. " f"It will be disallowed in Python 3.15." ) warnings.warn(depr_message, category=DeprecationWarning, stacklevel=3) class _Sentinel: __slots__ = () def __repr__(self): return '' _sentinel = _Sentinel() def _eval_type(t, globalns, localns, type_params=_sentinel, *, recursive_guard=frozenset(), format=annotationlib.Format.VALUE, owner=None): """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 type_params is _sentinel: _deprecation_warning_for_no_type_params_passed("typing._eval_type") type_params = () if isinstance(t, ForwardRef): # If the forward_ref has __forward_module__ set, evaluate() infers the globals # from the module, and it will probably pick better than the globals we have here. if t.__forward_module__ is not None: globalns = None return evaluate_forward_ref(t, globals=globalns, locals=localns, type_params=type_params, owner=owner, _recursive_guard=recursive_guard, format=format) if isinstance(t, (_GenericAlias, GenericAlias, types.UnionType)): if isinstance(t, GenericAlias): args = tuple( _make_forward_ref(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, type_params, recursive_guard=recursive_guard, format=format, owner=owner, ) 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 _TypedCacheSpecialForm(_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) @_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.', allow_special_forms=True) 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.', allow_special_forms=True) 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)] @_TypedCacheSpecialForm @_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 predicate functions. ``TypeGuard`` can be used to annotate the return type of a user-defined type predicate 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 predicate". Sometimes it would be convenient to use a user-defined boolean function as a type predicate. Such a function should use ``TypeGuard[...]`` or ``TypeIs[...]`` as its return type to alert static type checkers to this intention. ``TypeGuard`` should be used over ``TypeIs`` when narrowing from an incompatible type (e.g., ``list[object]`` to ``list[int]``) or when the function does not return ``True`` for all instances of the narrowed type. Using ``-> TypeGuard[NarrowedType]`` 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 ``NarrowedType``. For example:: def is_str_list(val: list[object]) -> TypeGuard[list[str]]: '''Determines whether all objects in the list are strings''' return all(isinstance(x, str) for x in val) def func1(val: list[object]): if is_str_list(val): # Type of ``val`` is narrowed to ``list[str]``. print(" ".join(val)) else: # Type of ``val`` remains as ``list[object]``. print("Not a list of strings!") 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 predicates 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,)) @_SpecialForm def TypeIs(self, parameters): """Special typing construct for marking user-defined type predicate functions. ``TypeIs`` can be used to annotate the return type of a user-defined type predicate function. ``TypeIs`` only accepts a single type argument. At runtime, functions marked this way should return a boolean and accept at least one argument. ``TypeIs`` 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 predicate". Sometimes it would be convenient to use a user-defined boolean function as a type predicate. Such a function should use ``TypeIs[...]`` or ``TypeGuard[...]`` as its return type to alert static type checkers to this intention. ``TypeIs`` usually has more intuitive behavior than ``TypeGuard``, but it cannot be used when the input and output types are incompatible (e.g., ``list[object]`` to ``list[int]``) or when the function does not return ``True`` for all instances of the narrowed type. Using ``-> TypeIs[NarrowedType]`` 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 intersection of the argument's original type and ``NarrowedType``. 3. If the return value is ``False``, the type of its argument is narrowed to exclude ``NarrowedType``. For example:: from typing import assert_type, final, TypeIs class Parent: pass class Child(Parent): pass @final class Unrelated: pass def is_parent(val: object) -> TypeIs[Parent]: return isinstance(val, Parent) def run(arg: Child | Unrelated): if is_parent(arg): # Type of ``arg`` is narrowed to the intersection # of ``Parent`` and ``Child``, which is equivalent to # ``Child``. assert_type(arg, Child) else: # Type of ``arg`` is narrowed to exclude ``Parent``, # so only ``Unrelated`` is left. assert_type(arg, Unrelated) The type inside ``TypeIs`` must be consistent with the type of the function's argument; if it is not, static type checkers will raise an error. An incorrectly written ``TypeIs`` function can lead to unsound behavior in the type system; it is the user's responsibility to write such functions in a type-safe manner. ``TypeIs`` also works with type variables. For more information, see PEP 742 (Narrowing types with ``TypeIs``). """ item = _type_check(parameters, f'{self} accepts only single type.') return _GenericAlias(self, (item,)) def _make_forward_ref(code, **kwargs): forward_ref = ForwardRef(code, **kwargs) # For compatibility, eagerly compile the forwardref's code. forward_ref.__forward_code__ return forward_ref def evaluate_forward_ref( forward_ref, *, owner=None, globals=None, locals=None, type_params=None, format=annotationlib.Format.VALUE, _recursive_guard=frozenset(), ): """Evaluate a forward reference as a type hint. This is similar to calling the ForwardRef.evaluate() method, but unlike that method, evaluate_forward_ref() also: * Recursively evaluates forward references nested within the type hint. * Rejects certain objects that are not valid type hints. * Replaces type hints that evaluate to None with types.NoneType. * Supports the *FORWARDREF* and *STRING* formats. *forward_ref* must be an instance of ForwardRef. *owner*, if given, should be the object that holds the annotations that the forward reference derived from, such as a module, class object, or function. It is used to infer the namespaces to use for looking up names. *globals* and *locals* can also be explicitly given to provide the global and local namespaces. *type_params* is a tuple of type parameters that are in scope when evaluating the forward reference. This parameter must be provided (though it may be an empty tuple) if *owner* is not given and the forward reference does not already have an owner set. *format* specifies the format of the annotation and is a member of the annotationlib.Format enum. """ if type_params is _sentinel: _deprecation_warning_for_no_type_params_passed("typing.evaluate_forward_ref") type_params = () if format == annotationlib.Format.STRING: return forward_ref.__forward_arg__ if forward_ref.__forward_arg__ in _recursive_guard: return forward_ref try: value = forward_ref.evaluate(globals=globals, locals=locals, type_params=type_params, owner=owner) except NameError: if format == annotationlib.Format.FORWARDREF: return forward_ref else: raise type_ = _type_check( value, "Forward references must evaluate to types.", is_argument=forward_ref.__forward_is_argument__, allow_special_forms=forward_ref.__forward_is_class__, ) return _eval_type( type_, globals, locals, type_params, recursive_guard=_recursive_guard | {forward_ref.__forward_arg__}, format=format, owner=owner, ) 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) 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}") if left == alen - right and self.has_default(): replacement = _unpack_args(self.__default__) else: replacement = args[left: alen - right] return ( *args[:left], *([fillarg]*(typevartuple_index - left)), replacement, *([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) and self.has_default(): args = [*args, self.__default__] 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, args): """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 `args=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(args, tuple): args = (args,) args = tuple(_type_convert(p) for p in args) 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 args: raise TypeError( f"Parameter list to {cls.__qualname__}[...] cannot be empty" ) if not all(_is_typevar_like(p) for p in args): raise TypeError( f"Parameters to {cls.__name__}[...] must all be type variables " f"or parameter specification variables.") if len(set(args)) != len(args): 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: args = prepare(cls, args) _check_generic_specialization(cls, args) new_args = [] for param, new_arg in zip(cls.__parameters__, args): if isinstance(param, TypeVarTuple): new_args.extend(new_arg) else: new_args.append(new_arg) args = tuple(new_args) return _GenericAlias(cls, args) 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_type_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 # Some objects raise TypeError (or something even more exotic) # if you try to set attributes on them; we guard against that here except Exception: pass return result def __mro_entries__(self, bases): res = [] if self.__origin__ not in bases: res.append(self.__origin__) # Check if any base that occurs after us in `bases` is either itself a # subclass of Generic, or something which will add a subclass of Generic # to `__bases__` via its `__mro_entries__`. If not, add Generic # ourselves. The goal is to ensure that Generic (or a subclass) will # appear exactly once in the final bases tuple. If we let it appear # multiple times, we risk "can't form a consistent MRO" errors. i = bases.index(self) for b in bases[i+1:]: if isinstance(b, _BaseGenericAlias): break if not isinstance(b, type): meth = getattr(b, "__mro_entries__", None) new_bases = meth(bases) if meth else None if ( isinstance(new_bases, tuple) and any( isinstance(b2, type) and issubclass(b2, Generic) for b2 in new_bases ) ): break elif 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', '_defaults'}: 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`, `TypeGuard`, and `TypeIs`: # # All _GenericAlias # Final[int] # ClassVar[float] # TypeGuard[bool] # TypeIs[range] 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) enforce_default_ordering = origin in (Generic, Protocol) self.__parameters__ = _collect_type_parameters( args, enforce_default_ordering=enforce_default_ordering, ) 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 = _unpack_args(*(_type_convert(p) for p in 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, defaults=()): if name is None: name = origin.__name__ super().__init__(origin, inst=inst, name=name) self._nparams = nparams self._defaults = defaults 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) if (self._defaults and len(params) < self._nparams and len(params) + len(self._defaults) >= self._nparams ): params = (*params, *self._defaults[len(params) - self._nparams:]) actual_len = len(params) if actual_len != self._nparams: if self._defaults: expected = f"at least {self._nparams - len(self._defaults)}" else: expected = str(self._nparams) if not self._nparams: raise TypeError(f"{self} is not a generic class") raise TypeError(f"Too {'many' if actual_len > self._nparams else 'few'} arguments for {self};" f" actual {actual_len}, expected {expected}") 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 _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 try: # fast path return set(self.__args__) == set(other.__args__) except TypeError: # not hashable, slow path return _compare_args_orderless(self.__args__, 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, types.GenericAlias)): if arg.__origin__ is not tuple: raise TypeError("Unpack[...] must be used with a tuple type") 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__', '__match_args__', '__static_attributes__', '__firstlineno__', '__annotate__', }) # 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 # Preload these once, as globals, as a micro-optimisation. # This makes a significant difference to the time it takes # to do `isinstance()`/`issubclass()` checks # against runtime-checkable protocols with only one callable member. _abc_instancecheck = ABCMeta.__instancecheck__ _abc_subclasscheck = ABCMeta.__subclasscheck__ def _type_check_issubclass_arg_1(arg): """Raise TypeError if `arg` is not an instance of `type` in `issubclass(arg, )`. In most cases, this is verified by type.__subclasscheck__. Checking it again unnecessarily would slow down issubclass() checks, so, we don't perform this check unless we absolutely have to. For various error paths, however, we want to ensure that *this* error message is shown to the user where relevant, rather than a typing.py-specific error message. """ if not isinstance(arg, type): # Same error message as for issubclass(1, int). raise TypeError('issubclass() arg 1 must be a class') 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 getattr(cls, '_is_runtime_protocol', False): _type_check_issubclass_arg_1(other) 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 ): _type_check_issubclass_arg_1(other) non_method_attrs = sorted(cls.__non_callable_proto_members__) raise TypeError( "Protocols with non-method members don't support issubclass()." f" Non-method members: {str(non_method_attrs)[1:-1]}." ) return _abc_subclasscheck(cls, 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 _abc_instancecheck(cls, 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 _abc_instancecheck(cls, 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 metadata. 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__,) @_TypedCacheSpecialForm @_tp_cache(typed=True) def Annotated(self, *params): """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. """ 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 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 def get_type_hints(obj, globalns=None, localns=None, include_extras=False, *, format=annotationlib.Format.VALUE): """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__): ann = annotationlib.get_annotations(base, format=format) if format is annotationlib.Format.STRING: hints.update(ann) continue if globalns is None: base_globals = getattr(sys.modules.get(base.__module__, None), '__dict__', {}) else: base_globals = globalns 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 = _make_forward_ref(value, is_argument=False, is_class=True) value = _eval_type(value, base_globals, base_locals, base.__type_params__, format=format, owner=obj) hints[name] = value if include_extras or format is annotationlib.Format.STRING: return hints else: return {k: _strip_annotations(t) for k, t in hints.items()} hints = annotationlib.get_annotations(obj, format=format) if ( not hints and not isinstance(obj, types.ModuleType) and not callable(obj) and not hasattr(obj, '__annotations__') and not hasattr(obj, '__annotate__') ): raise TypeError(f"{obj!r} is not a module, class, or callable.") if format is annotationlib.Format.STRING: return hints 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 type_params = getattr(obj, "__type_params__", ()) 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 = _make_forward_ref( value, is_argument=not isinstance(obj, types.ModuleType), is_class=False, ) hints[name] = _eval_type(value, globalns, localns, type_params, format=format, owner=obj) 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, ReadOnly): 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. """ import warnings warnings._deprecated("typing.no_type_check_decorator", remove=(3, 15)) @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) # 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) 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, defaults=(types.NoneType, types.NoneType)) AsyncGenerator = _alias(collections.abc.AsyncGenerator, 2, defaults=(types.NoneType,)) 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, fields, annotate_func, module, defaults = ()): nm_tpl = collections.namedtuple(name, fields, defaults=defaults, module=module) nm_tpl.__annotate__ = nm_tpl.__new__.__annotate__ = annotate_func return nm_tpl def _make_eager_annotate(types): checked_types = {key: _type_check(val, f"field {key} annotation must be a type") for key, val in types.items()} def annotate(format): if format in (annotationlib.Format.VALUE, annotationlib.Format.FORWARDREF): return checked_types else: return annotationlib.annotations_to_string(types) return annotate # 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__', '__annotate__'}) 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) if "__annotations__" in ns: types = ns["__annotations__"] field_names = list(types) annotate = _make_eager_annotate(types) elif "__annotate__" in ns: original_annotate = ns["__annotate__"] types = annotationlib.call_annotate_function(original_annotate, annotationlib.Format.FORWARDREF) field_names = list(types) # For backward compatibility, type-check all the types at creation time for typ in types.values(): _type_check(typ, "field annotation must be a type") def annotate(format): annos = annotationlib.call_annotate_function(original_annotate, format) if format != annotationlib.Format.STRING: return {key: _type_check(val, f"field {key} annotation must be a type") for key, val in annos.items()} return annos else: # Empty NamedTuple field_names = [] annotate = lambda format: {} default_names = [] for field_name in field_names: 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, field_names, annotate, 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, val in ns.items(): if key in _prohibited: raise AttributeError("Cannot overwrite NamedTuple attribute " + key) elif key not in _special: if key not in nm_tpl._fields: setattr(nm_tpl, key, val) try: set_name = type(val).__set_name__ except AttributeError: pass else: try: set_name(val, nm_tpl, key) except BaseException as e: e.add_note( f"Error calling __set_name__ on {type(val).__name__!r} " f"instance {key!r} in {typename!r}" ) raise if Generic in bases: nm_tpl.__init_subclass__() return nm_tpl def NamedTuple(typename, fields=_sentinel, /, **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 _sentinel: if kwargs: deprecated_thing = "Creating NamedTuple classes using keyword arguments" deprecation_msg = ( "{name} is deprecated and will be disallowed in Python {remove}. " "Use the class-based or functional syntax instead." ) else: deprecated_thing = "Failing to pass a value for the 'fields' parameter" example = f"`{typename} = NamedTuple({typename!r}, [])`" deprecation_msg = ( "{name} is deprecated and will be disallowed in Python {remove}. " "To create a NamedTuple class with 0 fields " "using the functional syntax, " "pass an empty list, e.g. " ) + example + "." elif fields is None: if kwargs: raise TypeError( "Cannot pass `None` as the 'fields' parameter " "and also specify fields using keyword arguments" ) else: deprecated_thing = "Passing `None` as the 'fields' parameter" example = f"`{typename} = NamedTuple({typename!r}, [])`" deprecation_msg = ( "{name} is deprecated and will be disallowed in Python {remove}. " "To create a NamedTuple class with 0 fields " "using the functional syntax, " "pass an empty list, e.g. " ) + example + "." elif kwargs: raise TypeError("Either list of fields or keywords" " can be provided to NamedTuple, not both") if fields is _sentinel or fields is None: import warnings warnings._deprecated(deprecated_thing, message=deprecation_msg, remove=(3, 15)) fields = kwargs.items() types = {n: _type_check(t, f"field {n} annotation must be a type") for n, t in fields} field_names = [n for n, _ in fields] nt = _make_nmtuple(typename, field_names, _make_eager_annotate(types), 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 def _get_typeddict_qualifiers(annotation_type): while True: 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] else: break elif annotation_origin is Required: yield Required (annotation_type,) = get_args(annotation_type) elif annotation_origin is NotRequired: yield NotRequired (annotation_type,) = get_args(annotation_type) elif annotation_origin is ReadOnly: yield ReadOnly (annotation_type,) = get_args(annotation_type) else: break 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 if "__annotations__" in ns: own_annotate = None own_annotations = ns["__annotations__"] elif "__annotate__" in ns: own_annotate = ns["__annotate__"] own_annotations = annotationlib.call_annotate_function( own_annotate, annotationlib.Format.FORWARDREF, owner=tp_dict ) else: own_annotate = None own_annotations = {} msg = "TypedDict('Name', {f0: t0, f1: t1, ...}); each t must be a type" own_checked_annotations = { n: _type_check(tp, msg, module=tp_dict.__module__) for n, tp in own_annotations.items() } required_keys = set() optional_keys = set() readonly_keys = set() mutable_keys = set() for base in bases: 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 readonly_keys.update(base.__dict__.get('__readonly_keys__', ())) mutable_keys.update(base.__dict__.get('__mutable_keys__', ())) for annotation_key, annotation_type in own_checked_annotations.items(): qualifiers = set(_get_typeddict_qualifiers(annotation_type)) if Required in qualifiers: is_required = True elif NotRequired in qualifiers: 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) if ReadOnly in qualifiers: if annotation_key in mutable_keys: raise TypeError( f"Cannot override mutable key {annotation_key!r}" " with read-only key" ) readonly_keys.add(annotation_key) else: mutable_keys.add(annotation_key) readonly_keys.discard(annotation_key) assert required_keys.isdisjoint(optional_keys), ( f"Required keys overlap with optional keys in {name}:" f" {required_keys=}, {optional_keys=}" ) def __annotate__(format): annos = {} for base in bases: if base is Generic: continue base_annotate = base.__annotate__ if base_annotate is None: continue base_annos = annotationlib.call_annotate_function(base.__annotate__, format, owner=base) annos.update(base_annos) if own_annotate is not None: own = annotationlib.call_annotate_function(own_annotate, format, owner=tp_dict) if format != annotationlib.Format.STRING: own = { n: _type_check(tp, msg, module=tp_dict.__module__) for n, tp in own.items() } elif format == annotationlib.Format.STRING: own = annotationlib.annotations_to_string(own_annotations) else: own = own_checked_annotations annos.update(own) return annos tp_dict.__annotate__ = __annotate__ tp_dict.__required_keys__ = frozenset(required_keys) tp_dict.__optional_keys__ = frozenset(optional_keys) tp_dict.__readonly_keys__ = frozenset(readonly_keys) tp_dict.__mutable_keys__ = frozenset(mutable_keys) 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=_sentinel, /, *, total=True): """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. The ReadOnly special form can be used to mark individual keys as immutable for type checkers:: class DatabaseUser(TypedDict): id: ReadOnly[int] # the "id" key must not be modified username: str # the "username" key can be changed """ if fields is _sentinel or fields is None: import warnings if fields is _sentinel: deprecated_thing = "Failing to pass a value for the 'fields' parameter" else: deprecated_thing = "Passing `None` as the 'fields' parameter" example = f"`{typename} = TypedDict({typename!r}, {{{{}}}})`" deprecation_msg = ( "{name} is deprecated and will be disallowed in Python {remove}. " "To create a TypedDict class with 0 fields " "using the functional syntax, " "pass an empty dictionary, e.g. " ) + example + "." warnings._deprecated(deprecated_thing, message=deprecation_msg, remove=(3, 15)) fields = {} 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,)) @_SpecialForm def ReadOnly(self, parameters): """A special typing construct to mark an item of a TypedDict as read-only. For example:: class Movie(TypedDict): title: ReadOnly[str] year: int def mutate_movie(m: Movie) -> None: m["year"] = 1992 # allowed m["title"] = "The Matrix" # typechecker error There is no runtime checking for this property. """ 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 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 def is_protocol(tp: type, /) -> bool: """Return True if the given type is a Protocol. Example:: >>> from typing import Protocol, is_protocol >>> class P(Protocol): ... def a(self) -> str: ... ... b: int >>> is_protocol(P) True >>> is_protocol(int) False """ return ( isinstance(tp, type) and getattr(tp, '_is_protocol', False) and tp != Protocol ) def get_protocol_members(tp: type, /) -> frozenset[str]: """Return the set of members defined in a Protocol. Example:: >>> from typing import Protocol, get_protocol_members >>> class P(Protocol): ... def a(self) -> str: ... ... b: int >>> get_protocol_members(P) == frozenset({'a', 'b'}) True Raise a TypeError for arguments that are not Protocols. """ if not is_protocol(tp): raise TypeError(f'{tp!r} is not a Protocol') return frozenset(tp.__protocol_attrs__) def __getattr__(attr): """Improve the import time of the typing module. Soft-deprecated objects which are costly to create are only created on-demand here. """ if attr in {"Pattern", "Match"}: import re obj = _alias(getattr(re, attr), 1) elif attr in {"ContextManager", "AsyncContextManager"}: import contextlib obj = _alias(getattr(contextlib, f"Abstract{attr}"), 2, name=attr, defaults=(bool | None,)) elif attr == "_collect_parameters": import warnings depr_message = ( "The private _collect_parameters function is deprecated and will be" " removed in a future version of Python. Any use of private functions" " is discouraged and may break in the future." ) warnings.warn(depr_message, category=DeprecationWarning, stacklevel=2) obj = _collect_type_parameters else: raise AttributeError(f"module {__name__!r} has no attribute {attr!r}") globals()[attr] = obj return obj