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2210 lines (1762 loc) · 73.1 KB
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"""
The typing module: Support for gradual typing as defined by PEP 484.
At large scale, the structure of the module is following:
* Imports and exports, all public names should be explicitly added to __all__.
* Internal helper functions: these should never be used in code outside this module.
* _SpecialForm and its instances (special forms): Any, NoReturn, ClassVar, Union, Optional
* Two classes whose instances can be type arguments in addition to types: ForwardRef and TypeVar
* The core of internal generics API: _GenericAlias and _VariadicGenericAlias, the latter is
currently only used by Tuple and Callable. All subscripted types like X[int], Union[int, str],
etc., are instances of either of these classes.
* The public counterpart of the generics API consists of two classes: Generic and Protocol.
* Public helper functions: get_type_hints, overload, cast, no_type_check,
no_type_check_decorator.
* Generic aliases for collections.abc ABCs and few additional protocols.
* Special types: NewType, NamedTuple, TypedDict.
* Wrapper submodules for re and io related types.
"""
from abc import abstractmethod, ABCMeta
import collections
import collections.abc
import contextlib
import functools
import operator
import re as stdlib_re # Avoid confusion with the re we export.
import sys
import types
from types import WrapperDescriptorType, MethodWrapperType, MethodDescriptorType, GenericAlias
# Please keep __all__ alphabetized within each category.
__all__ = [
# Super-special typing primitives.
'Annotated',
'Any',
'Callable',
'ClassVar',
'Final',
'ForwardRef',
'Generic',
'Literal',
'Optional',
'Protocol',
'Tuple',
'Type',
'TypeVar',
'Union',
# ABCs (from collections.abc).
'AbstractSet', # collections.abc.Set.
'ByteString',
'Container',
'ContextManager',
'Hashable',
'ItemsView',
'Iterable',
'Iterator',
'KeysView',
'Mapping',
'MappingView',
'MutableMapping',
'MutableSequence',
'MutableSet',
'Sequence',
'Sized',
'ValuesView',
'Awaitable',
'AsyncIterator',
'AsyncIterable',
'Coroutine',
'Collection',
'AsyncGenerator',
'AsyncContextManager',
# Structural checks, a.k.a. protocols.
'Reversible',
'SupportsAbs',
'SupportsBytes',
'SupportsComplex',
'SupportsFloat',
'SupportsIndex',
'SupportsInt',
'SupportsRound',
# Concrete collection types.
'ChainMap',
'Counter',
'Deque',
'Dict',
'DefaultDict',
'List',
'OrderedDict',
'Set',
'FrozenSet',
'NamedTuple', # Not really a type.
'TypedDict', # Not really a type.
'Generator',
# One-off things.
'AnyStr',
'cast',
'final',
'get_args',
'get_origin',
'get_type_hints',
'NewType',
'no_type_check',
'no_type_check_decorator',
'NoReturn',
'overload',
'runtime_checkable',
'Text',
'TYPE_CHECKING',
]
# The pseudo-submodules 're' and 'io' are part of the public
# namespace, but excluded from __all__ because they might stomp on
# legitimate imports of those modules.
def _type_convert(arg):
"""For converting None to type(None), and strings to ForwardRef."""
if arg is None:
return type(None)
if isinstance(arg, str):
return ForwardRef(arg)
return arg
def _type_check(arg, msg, is_argument=True):
"""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 is_argument:
invalid_generic_forms = invalid_generic_forms + (ClassVar, Final)
arg = _type_convert(arg)
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, NoReturn):
return arg
if isinstance(arg, _SpecialForm) or arg in (Generic, Protocol):
raise TypeError(f"Plain {arg} is not valid as type argument")
if isinstance(arg, (type, TypeVar, ForwardRef)):
return arg
if not callable(arg):
raise TypeError(f"{msg} Got {arg!r:.100}.")
return arg
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, types.GenericAlias):
return repr(obj)
if isinstance(obj, type):
if obj.__module__ == 'builtins':
return obj.__qualname__
return f'{obj.__module__}.{obj.__qualname__}'
if obj is ...:
return('...')
if isinstance(obj, types.FunctionType):
return obj.__name__
return repr(obj)
def _collect_type_vars(types):
"""Collect all type variable contained in types in order of
first appearance (lexicographic order). For example::
_collect_type_vars((T, List[S, T])) == (T, S)
"""
tvars = []
for t in types:
if isinstance(t, TypeVar) and t not in tvars:
tvars.append(t)
if isinstance(t, (_GenericAlias, GenericAlias)):
tvars.extend([t for t in t.__parameters__ if t not in tvars])
return tuple(tvars)
def _check_generic(cls, parameters, elen):
"""Check correct count for parameters of a generic cls (internal helper).
This gives a nice error message in case of count mismatch.
"""
if not elen:
raise TypeError(f"{cls} is not a generic class")
alen = len(parameters)
if alen != elen:
raise TypeError(f"Too {'many' if alen > elen else 'few'} parameters for {cls};"
f" actual {alen}, expected {elen}")
def _deduplicate(params):
# Weed out strict duplicates, preserving the first of each occurrence.
all_params = set(params)
if len(all_params) < len(params):
new_params = []
for t in params:
if t in all_params:
new_params.append(t)
all_params.remove(t)
params = new_params
assert not all_params, all_params
return params
def _remove_dups_flatten(parameters):
"""An 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):
params.extend(p.__args__)
elif isinstance(p, tuple) and len(p) > 0 and p[0] is Union:
params.extend(p[1:])
else:
params.append(p)
return tuple(_deduplicate(params))
def _flatten_literal_params(parameters):
"""An 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 = []
def _tp_cache(func=None, /, *, typed=False):
"""Internal wrapper caching __getitem__ of generic types with a fallback to
original function for non-hashable arguments.
"""
def decorator(func):
cached = functools.lru_cache(typed=typed)(func)
_cleanups.append(cached.cache_clear)
@functools.wraps(func)
def inner(*args, **kwds):
try:
return cached(*args, **kwds)
except TypeError:
pass # All real errors (not unhashable args) are raised below.
return func(*args, **kwds)
return inner
if func is not None:
return decorator(func)
return decorator
def _eval_type(t, globalns, localns, recursive_guard=frozenset()):
"""Evaluate all forward references in the given type t.
For use of globalns and localns see the docstring for get_type_hints().
recursive_guard is used to prevent prevent infinite recursion
with recursive ForwardRef.
"""
if isinstance(t, ForwardRef):
return t._evaluate(globalns, localns, recursive_guard)
if isinstance(t, (_GenericAlias, GenericAlias)):
ev_args = tuple(_eval_type(a, globalns, localns, recursive_guard) for a in t.__args__)
if ev_args == t.__args__:
return t
if isinstance(t, GenericAlias):
return GenericAlias(t.__origin__, ev_args)
else:
return t.copy_with(ev_args)
return t
class _Final:
"""Mixin to prohibit subclassing"""
__slots__ = ('__weakref__',)
def __init_subclass__(self, /, *args, **kwds):
if '_root' not in kwds:
raise TypeError("Cannot subclass special typing classes")
class _Immutable:
"""Mixin to indicate that object should not be copied."""
__slots__ = ()
def __copy__(self):
return self
def __deepcopy__(self, memo):
return self
# Internal indicator of special typing constructs.
# See __doc__ instance attribute for specific docs.
class _SpecialForm(_Final, _root=True):
__slots__ = ('_name', '__doc__', '_getitem')
def __init__(self, getitem):
self._getitem = getitem
self._name = getitem.__name__
self.__doc__ = getitem.__doc__
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 __instancecheck__(self, obj):
raise TypeError(f"{self} cannot be used with isinstance()")
def __subclasscheck__(self, cls):
raise TypeError(f"{self} cannot be used with issubclass()")
@_tp_cache
def __getitem__(self, parameters):
return self._getitem(self, parameters)
class _LiteralSpecialForm(_SpecialForm, _root=True):
@_tp_cache(typed=True)
def __getitem__(self, parameters):
return self._getitem(self, parameters)
@_SpecialForm
def Any(self, parameters):
"""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
or class checks.
"""
raise TypeError(f"{self} is not subscriptable")
@_SpecialForm
def NoReturn(self, parameters):
"""Special type indicating functions that never return.
Example::
from typing import NoReturn
def stop() -> NoReturn:
raise Exception('no way')
This type is invalid in other positions, e.g., ``List[NoReturn]``
will fail in static type checkers.
"""
raise TypeError(f"{self} is not subscriptable")
@_SpecialForm
def ClassVar(self, parameters):
"""Special type construct to mark class variables.
An annotation wrapped in ClassVar indicates that a given
attribute is intended to be used as a class variable and
should not be set on instances of that class. Usage::
class Starship:
stats: ClassVar[Dict[str, int]] = {} # class variable
damage: int = 10 # instance variable
ClassVar accepts only types and cannot be further subscribed.
Note that ClassVar is not a class itself, and should not
be used with isinstance() or issubclass().
"""
item = _type_check(parameters, f'{self} accepts only single type.')
return _GenericAlias(self, (item,))
@_SpecialForm
def Final(self, parameters):
"""Special typing construct to indicate final names to type checkers.
A final name cannot be re-assigned or overridden in a subclass.
For example:
MAX_SIZE: Final = 9000
MAX_SIZE += 1 # Error reported by type checker
class Connection:
TIMEOUT: Final[int] = 10
class FastConnector(Connection):
TIMEOUT = 1 # Error reported by type checker
There is no runtime checking of these properties.
"""
item = _type_check(parameters, f'{self} accepts only single type.')
return _GenericAlias(self, (item,))
@_SpecialForm
def Union(self, parameters):
"""Union type; Union[X, Y] means either X or Y.
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.::
Union[Union[int, str], float] == Union[int, str, float]
- Unions of a single argument vanish, e.g.::
Union[int] == int # The constructor actually returns int
- Redundant arguments are skipped, e.g.::
Union[int, str, int] == Union[int, str]
- When comparing unions, the argument order is ignored, e.g.::
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]
return _UnionGenericAlias(self, parameters)
@_SpecialForm
def Optional(self, parameters):
"""Optional type.
Optional[X] is equivalent to Union[X, None].
"""
arg = _type_check(parameters, f"{self} requires a single type.")
return Union[arg, type(None)]
@_LiteralSpecialForm
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.
if not isinstance(parameters, tuple):
parameters = (parameters,)
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)
class ForwardRef(_Final, _root=True):
"""Internal wrapper to hold a forward reference."""
__slots__ = ('__forward_arg__', '__forward_code__',
'__forward_evaluated__', '__forward_value__',
'__forward_is_argument__')
def __init__(self, arg, is_argument=True):
if not isinstance(arg, str):
raise TypeError(f"Forward reference must be a string -- got {arg!r}")
try:
code = compile(arg, '<string>', 'eval')
except SyntaxError:
raise SyntaxError(f"Forward reference must be an expression -- got {arg!r}")
self.__forward_arg__ = arg
self.__forward_code__ = code
self.__forward_evaluated__ = False
self.__forward_value__ = None
self.__forward_is_argument__ = is_argument
def _evaluate(self, globalns, localns, recursive_guard):
if self.__forward_arg__ in recursive_guard:
return self
if not self.__forward_evaluated__ or localns is not globalns:
if globalns is None and localns is None:
globalns = localns = {}
elif globalns is None:
globalns = localns
elif localns is None:
localns = globalns
type_ =_type_check(
eval(self.__forward_code__, globalns, localns),
"Forward references must evaluate to types.",
is_argument=self.__forward_is_argument__,
)
self.__forward_value__ = _eval_type(
type_, globalns, localns, recursive_guard | {self.__forward_arg__}
)
self.__forward_evaluated__ = True
return self.__forward_value__
def __eq__(self, other):
if not isinstance(other, ForwardRef):
return NotImplemented
if self.__forward_evaluated__ and other.__forward_evaluated__:
return (self.__forward_arg__ == other.__forward_arg__ and
self.__forward_value__ == other.__forward_value__)
return self.__forward_arg__ == other.__forward_arg__
def __hash__(self):
return hash(self.__forward_arg__)
def __repr__(self):
return f'ForwardRef({self.__forward_arg__!r})'
class TypeVar(_Final, _Immutable, _root=True):
"""Type variable.
Usage::
T = TypeVar('T') # Can be anything
A = TypeVar('A', str, bytes) # Must be str or bytes
Type variables exist primarily for the benefit of static type
checkers. They serve as the parameters for generic types as well
as for generic function definitions. See class Generic for more
information on generic types. Generic functions work as follows:
def repeat(x: T, n: int) -> List[T]:
'''Return a list containing n references to x.'''
return [x]*n
def longest(x: A, y: A) -> A:
'''Return the longest of two strings.'''
return x if len(x) >= len(y) else y
The latter example's signature is essentially the overloading
of (str, str) -> str and (bytes, bytes) -> bytes. Also note
that if the arguments are instances of some subclass of str,
the return type is still plain str.
At runtime, isinstance(x, T) and issubclass(C, T) will raise TypeError.
Type variables defined with covariant=True or contravariant=True
can be used to declare covariant or contravariant generic types.
See PEP 484 for more details. By default generic types are invariant
in all type variables.
Type variables can be introspected. e.g.:
T.__name__ == 'T'
T.__constraints__ == ()
T.__covariant__ == False
T.__contravariant__ = False
A.__constraints__ == (str, bytes)
Note that only type variables defined in global scope can be pickled.
"""
__slots__ = ('__name__', '__bound__', '__constraints__',
'__covariant__', '__contravariant__', '__dict__')
def __init__(self, name, *constraints, bound=None,
covariant=False, contravariant=False):
self.__name__ = name
if covariant and contravariant:
raise ValueError("Bivariant types are not supported.")
self.__covariant__ = bool(covariant)
self.__contravariant__ = bool(contravariant)
if constraints and bound is not None:
raise TypeError("Constraints cannot be combined with bound=...")
if constraints and len(constraints) == 1:
raise TypeError("A single constraint is not allowed")
msg = "TypeVar(name, constraint, ...): constraints must be types."
self.__constraints__ = tuple(_type_check(t, msg) for t in constraints)
if bound:
self.__bound__ = _type_check(bound, "Bound must be a type.")
else:
self.__bound__ = None
try:
def_mod = sys._getframe(1).f_globals.get('__name__', '__main__') # for pickling
except (AttributeError, ValueError):
def_mod = None
if def_mod != 'typing':
self.__module__ = def_mod
def __repr__(self):
if self.__covariant__:
prefix = '+'
elif self.__contravariant__:
prefix = '-'
else:
prefix = '~'
return prefix + self.__name__
def __reduce__(self):
return self.__name__
def _is_dunder(attr):
return attr.startswith('__') and attr.endswith('__')
class _BaseGenericAlias(_Final, _root=True):
"""The central part of internal API.
This represents a generic version of type 'origin' with type arguments 'params'.
There are two kind of these aliases: user defined and special. The special ones
are wrappers around builtin collections and ABCs in collections.abc. These must
have 'name' always set. If 'inst' is False, then the alias can't be instantiated,
this is used by e.g. typing.List and typing.Dict.
"""
def __init__(self, origin, *, inst=True, name=None):
self._inst = inst
self._name = name
self.__origin__ = origin
self.__slots__ = None # This is not documented.
def __call__(self, *args, **kwargs):
if not self._inst:
raise TypeError(f"Type {self._name} cannot be instantiated; "
f"use {self.__origin__.__name__}() instead")
result = self.__origin__(*args, **kwargs)
try:
result.__orig_class__ = self
except AttributeError:
pass
return result
def __mro_entries__(self, bases):
res = []
if self.__origin__ not in bases:
res.append(self.__origin__)
i = bases.index(self)
for b in bases[i+1:]:
if isinstance(b, _BaseGenericAlias) or issubclass(b, Generic):
break
else:
res.append(Generic)
return tuple(res)
def __getattr__(self, attr):
# We are careful for copy and pickle.
# Also for simplicity we just don't relay all dunder names
if '__origin__' in self.__dict__ and not _is_dunder(attr):
return getattr(self.__origin__, attr)
raise AttributeError(attr)
def __setattr__(self, attr, val):
if _is_dunder(attr) or attr in ('_name', '_inst', '_nparams'):
super().__setattr__(attr, val)
else:
setattr(self.__origin__, attr, val)
def __instancecheck__(self, obj):
return self.__subclasscheck__(type(obj))
def __subclasscheck__(self, cls):
raise TypeError("Subscripted generics cannot be used with"
" class and instance checks")
# 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):
def __init__(self, origin, params, *, inst=True, name=None):
super().__init__(origin, inst=inst, name=name)
if not isinstance(params, tuple):
params = (params,)
self.__args__ = tuple(... if a is _TypingEllipsis else
() if a is _TypingEmpty else
a for a in params)
self.__parameters__ = _collect_type_vars(params)
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__))
@_tp_cache
def __getitem__(self, params):
if self.__origin__ in (Generic, Protocol):
# Can't subscript Generic[...] or Protocol[...].
raise TypeError(f"Cannot subscript already-subscripted {self}")
if not isinstance(params, tuple):
params = (params,)
msg = "Parameters to generic types must be types."
params = tuple(_type_check(p, msg) for p in params)
_check_generic(self, params, len(self.__parameters__))
subst = dict(zip(self.__parameters__, params))
new_args = []
for arg in self.__args__:
if isinstance(arg, TypeVar):
arg = subst[arg]
elif isinstance(arg, (_GenericAlias, GenericAlias)):
subparams = arg.__parameters__
if subparams:
subargs = tuple(subst[x] for x in subparams)
arg = arg[subargs]
new_args.append(arg)
return self.copy_with(tuple(new_args))
def copy_with(self, params):
return self.__class__(self.__origin__, params, name=self._name, inst=self._inst)
def __repr__(self):
if self._name:
name = 'typing.' + self._name
else:
name = _type_repr(self.__origin__)
args = ", ".join([_type_repr(a) for a in self.__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 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__,)
# _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(_BaseGenericAlias, _root=True):
def __init__(self, origin, nparams, *, inst=True, name=None):
if name is None:
name = origin.__name__
super().__init__(origin, inst=inst, name=name)
self._nparams = nparams
if origin.__module__ == 'builtins':
self.__doc__ = f'A generic version of {origin.__qualname__}.'
else:
self.__doc__ = f'A generic version of {origin.__module__}.{origin.__qualname__}.'
@_tp_cache
def __getitem__(self, params):
if not isinstance(params, tuple):
params = (params,)
msg = "Parameters to generic types must be types."
params = tuple(_type_check(p, msg) for p in params)
_check_generic(self, params, self._nparams)
return self.copy_with(params)
def copy_with(self, params):
return _GenericAlias(self.__origin__, params,
name=self._name, inst=self._inst)
def __repr__(self):
return 'typing.' + self._name
def __subclasscheck__(self, cls):
if isinstance(cls, _SpecialGenericAlias):
return issubclass(cls.__origin__, self.__origin__)
if not isinstance(cls, _GenericAlias):
return issubclass(cls, self.__origin__)
return super().__subclasscheck__(cls)
def __reduce__(self):
return self._name
class _CallableGenericAlias(_GenericAlias, _root=True):
def __repr__(self):
assert self._name == 'Callable'
if len(self.__args__) == 2 and self.__args__[0] is Ellipsis:
return super().__repr__()
return (f'typing.Callable'
f'[[{", ".join([_type_repr(a) for a in self.__args__[:-1]])}], '
f'{_type_repr(self.__args__[-1])}]')
def __reduce__(self):
args = self.__args__
if not (len(args) == 2 and args[0] is ...):
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 params == ():
return self.copy_with((_TypingEmpty,))
if not isinstance(params, tuple):
params = (params,)
if len(params) == 2 and params[1] is ...:
msg = "Tuple[t, ...]: t must be a type."
p = _type_check(params[0], msg)
return self.copy_with((p, _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(_GenericAlias, _root=True):
def copy_with(self, params):
return Union[params]
def __eq__(self, other):
if not isinstance(other, _UnionGenericAlias):
return NotImplemented
return set(self.__args__) == set(other.__args__)
def __hash__(self):
return hash(frozenset(self.__args__))
def __repr__(self):
args = self.__args__
if len(args) == 2:
if args[0] is type(None):
return f'typing.Optional[{_type_repr(args[1])}]'
elif args[1] is type(None):
return f'typing.Optional[{_type_repr(args[0])}]'
return super().__repr__()
def _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 Generic:
"""Abstract base class for generic types.
A generic type is typically declared by inheriting from
this class parameterized with one or more type variables.
For example, a generic mapping type might be defined as::
class Mapping(Generic[KT, VT]):
def __getitem__(self, key: KT) -> VT:
...
# Etc.
This class can then be used as follows::
def lookup_name(mapping: Mapping[KT, VT], key: KT, default: VT) -> VT:
try:
return mapping[key]
except KeyError:
return default
"""
__slots__ = ()
_is_protocol = False
@_tp_cache
def __class_getitem__(cls, params):
if not isinstance(params, tuple):
params = (params,)
if not params and cls is not Tuple:
raise TypeError(
f"Parameter list to {cls.__qualname__}[...] cannot be empty")
msg = "Parameters to generic types must be types."
params = tuple(_type_check(p, msg) for p in params)
if cls in (Generic, Protocol):
# Generic and Protocol can only be subscripted with unique type variables.
if not all(isinstance(p, TypeVar) for p in params):
raise TypeError(
f"Parameters to {cls.__name__}[...] must all be type variables")
if len(set(params)) != len(params):
raise TypeError(
f"Parameters to {cls.__name__}[...] must all be unique")
else:
# Subscripting a regular Generic subclass.
_check_generic(cls, params, len(cls.__parameters__))
return _GenericAlias(cls, params)
def __init_subclass__(cls, *args, **kwargs):
super().__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'
if error:
raise TypeError("Cannot inherit from plain Generic")
if '__orig_bases__' in cls.__dict__:
tvars = _collect_type_vars(cls.__orig_bases__)