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Edit File: typing.py

import abc from abc import abstractmethod, abstractproperty import collections import contextlib import functools import re as stdlib_re # Avoid confusion with the re we export. import sys import types try: import collections.abc as collections_abc except ImportError: import collections as collections_abc # Fallback for PY3.2. # Please keep __all__ alphabetized within each category. __all__ = [ # Super-special typing primitives. 'Any', 'Callable', 'ClassVar', 'Generic', 'Optional', 'Tuple', 'Type', 'TypeVar', 'Union', # ABCs (from collections.abc). 'AbstractSet', # collections.abc.Set. 'ByteString', 'Container', 'Hashable', 'ItemsView', 'Iterable', 'Iterator', 'KeysView', 'Mapping', 'MappingView', 'MutableMapping', 'MutableSequence', 'MutableSet', 'Sequence', 'Sized', 'ValuesView', # The following are added depending on presence # of their non-generic counterparts in stdlib: # Awaitable, # AsyncIterator, # AsyncIterable, # Coroutine, # Collection, # ContextManager # Structural checks, a.k.a. protocols. 'Reversible', 'SupportsAbs', 'SupportsFloat', 'SupportsInt', 'SupportsRound', # Concrete collection types. 'Dict', 'DefaultDict', 'List', 'Set', 'FrozenSet', 'NamedTuple', # Not really a type. 'Generator', # One-off things. 'AnyStr', 'cast', 'get_type_hints', 'NewType', 'no_type_check', 'no_type_check_decorator', 'overload', '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 _qualname(x): if sys.version_info[:2] >= (3, 3): return x.__qualname__ else: # Fall back to just name. return x.__name__ def _trim_name(nm): if nm.startswith('_') and nm not in ('_TypeAlias', '_ForwardRef', '_TypingBase', '_FinalTypingBase'): nm = nm[1:] return nm class TypingMeta(type): """Metaclass for most types defined in typing module (not a part of public API). This overrides __new__() to require an extra keyword parameter '_root', which serves as a guard against naive subclassing of the typing classes. Any legitimate class defined using a metaclass derived from TypingMeta must pass _root=True. This also defines a dummy constructor (all the work for most typing constructs is done in __new__) and a nicer repr(). """ _is_protocol = False def __new__(cls, name, bases, namespace, *, _root=False): if not _root: raise TypeError("Cannot subclass %s" % (', '.join(map(_type_repr, bases)) or '()')) return super().__new__(cls, name, bases, namespace) def __init__(self, *args, **kwds): pass def _eval_type(self, globalns, localns): """Override this in subclasses to interpret forward references. For example, List['C'] is internally stored as List[_ForwardRef('C')], which should evaluate to List[C], where C is an object found in globalns or localns (searching localns first, of course). """ return self def _get_type_vars(self, tvars): pass def __repr__(self): qname = _trim_name(_qualname(self)) return '%s.%s' % (self.__module__, qname) class _TypingBase(metaclass=TypingMeta, _root=True): """Internal indicator of special typing constructs.""" __slots__ = () def __init__(self, *args, **kwds): pass def __new__(cls, *args, **kwds): """Constructor. This only exists to give a better error message in case someone tries to subclass a special typing object (not a good idea). """ if (len(args) == 3 and isinstance(args[0], str) and isinstance(args[1], tuple)): # Close enough. raise TypeError("Cannot subclass %r" % cls) return super().__new__(cls) # Things that are not classes also need these. def _eval_type(self, globalns, localns): return self def _get_type_vars(self, tvars): pass def __repr__(self): cls = type(self) qname = _trim_name(_qualname(cls)) return '%s.%s' % (cls.__module__, qname) def __call__(self, *args, **kwds): raise TypeError("Cannot instantiate %r" % type(self)) class _FinalTypingBase(_TypingBase, _root=True): """Internal mix-in class to prevent instantiation. Prevents instantiation unless _root=True is given in class call. It is used to create pseudo-singleton instances Any, Union, Optional, etc. """ __slots__ = () def __new__(cls, *args, _root=False, **kwds): self = super().__new__(cls, *args, **kwds) if _root is True: return self raise TypeError("Cannot instantiate %r" % cls) def __reduce__(self): return _trim_name(type(self).__name__) class _ForwardRef(_TypingBase, _root=True): """Internal wrapper to hold a forward reference.""" __slots__ = ('__forward_arg__', '__forward_code__', '__forward_evaluated__', '__forward_value__') def __init__(self, arg): super().__init__(arg) if not isinstance(arg, str): raise TypeError('Forward reference must be a string -- got %r' % (arg,)) try: code = compile(arg, '<string>', 'eval') except SyntaxError: raise SyntaxError('Forward reference must be an expression -- got %r' % (arg,)) self.__forward_arg__ = arg self.__forward_code__ = code self.__forward_evaluated__ = False self.__forward_value__ = None def _eval_type(self, globalns, localns): 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 self.__forward_value__ = _type_check( eval(self.__forward_code__, globalns, localns), "Forward references must evaluate to types.") self.__forward_evaluated__ = True return self.__forward_value__ def __eq__(self, other): if not isinstance(other, _ForwardRef): return NotImplemented return (self.__forward_arg__ == other.__forward_arg__ and self.__forward_value__ == other.__forward_value__) def __hash__(self): return hash((self.__forward_arg__, self.__forward_value__)) def __instancecheck__(self, obj): raise TypeError("Forward references cannot be used with isinstance().") def __subclasscheck__(self, cls): raise TypeError("Forward references cannot be used with issubclass().") def __repr__(self): return '_ForwardRef(%r)' % (self.__forward_arg__,) class _TypeAlias(_TypingBase, _root=True): """Internal helper class for defining generic variants of concrete types. Note that this is not a type; let's call it a pseudo-type. It cannot be used in instance and subclass checks in parameterized form, i.e. ``isinstance(42, Match[str])`` raises ``TypeError`` instead of returning ``False``. """ __slots__ = ('name', 'type_var', 'impl_type', 'type_checker') def __init__(self, name, type_var, impl_type, type_checker): """Initializer. Args: name: The name, e.g. 'Pattern'. type_var: The type parameter, e.g. AnyStr, or the specific type, e.g. str. impl_type: The implementation type. type_checker: Function that takes an impl_type instance. and returns a value that should be a type_var instance. """ assert isinstance(name, str), repr(name) assert isinstance(impl_type, type), repr(impl_type) assert not isinstance(impl_type, TypingMeta), repr(impl_type) assert isinstance(type_var, (type, _TypingBase)), repr(type_var) self.name = name self.type_var = type_var self.impl_type = impl_type self.type_checker = type_checker def __repr__(self): return "%s[%s]" % (self.name, _type_repr(self.type_var)) def __getitem__(self, parameter): if not isinstance(self.type_var, TypeVar): raise TypeError("%s cannot be further parameterized." % self) if self.type_var.__constraints__ and isinstance(parameter, type): if not issubclass(parameter, self.type_var.__constraints__): raise TypeError("%s is not a valid substitution for %s." % (parameter, self.type_var)) if isinstance(parameter, TypeVar) and parameter is not self.type_var: raise TypeError("%s cannot be re-parameterized." % self) return self.__class__(self.name, parameter, self.impl_type, self.type_checker) def __eq__(self, other): if not isinstance(other, _TypeAlias): return NotImplemented return self.name == other.name and self.type_var == other.type_var def __hash__(self): return hash((self.name, self.type_var)) def __instancecheck__(self, obj): if not isinstance(self.type_var, TypeVar): raise TypeError("Parameterized type aliases cannot be used " "with isinstance().") return isinstance(obj, self.impl_type) def __subclasscheck__(self, cls): if not isinstance(self.type_var, TypeVar): raise TypeError("Parameterized type aliases cannot be used " "with issubclass().") return issubclass(cls, self.impl_type) def _get_type_vars(types, tvars): for t in types: if isinstance(t, TypingMeta) or isinstance(t, _TypingBase): t._get_type_vars(tvars) def _type_vars(types): tvars = [] _get_type_vars(types, tvars) return tuple(tvars) def _eval_type(t, globalns, localns): if isinstance(t, TypingMeta) or isinstance(t, _TypingBase): return t._eval_type(globalns, localns) return t def _type_check(arg, msg): """Check that the argument is a type, and return it (internal helper). As a special case, accept None and return type(None) instead. Also, _TypeAlias instances (e.g. Match, Pattern) are acceptable. 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). """ if arg is None: return type(None) if isinstance(arg, str): arg = _ForwardRef(arg) if (isinstance(arg, _TypingBase) and type(arg).__name__ == '_ClassVar' or not isinstance(arg, (type, _TypingBase)) and not callable(arg)): raise TypeError(msg + " Got %.100r." % (arg,)) # Bare Union etc. are not valid as type arguments if (type(arg).__name__ in ('_Union', '_Optional') and not getattr(arg, '__origin__', None) or isinstance(arg, TypingMeta) and _gorg(arg) in (Generic, _Protocol)): raise TypeError("Plain %s is not valid as type argument" % arg) 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, type) and not isinstance(obj, TypingMeta): if obj.__module__ == 'builtins': return _qualname(obj) return '%s.%s' % (obj.__module__, _qualname(obj)) if obj is ...: return('...') if isinstance(obj, types.FunctionType): return obj.__name__ return repr(obj) class _Any(_FinalTypingBase, _root=True): """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. """ __slots__ = () def __instancecheck__(self, obj): raise TypeError("Any cannot be used with isinstance().") def __subclasscheck__(self, cls): raise TypeError("Any cannot be used with issubclass().") Any = _Any(_root=True) class TypeVar(_TypingBase, _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 do 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) """ __slots__ = ('__name__', '__bound__', '__constraints__', '__covariant__', '__contravariant__') def __init__(self, name, *constraints, bound=None, covariant=False, contravariant=False): super().__init__(name, *constraints, bound=bound, covariant=covariant, contravariant=contravariant) 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 def _get_type_vars(self, tvars): if self not in tvars: tvars.append(self) def __repr__(self): if self.__covariant__: prefix = '+' elif self.__contravariant__: prefix = '-' else: prefix = '~' return prefix + self.__name__ def __instancecheck__(self, instance): raise TypeError("Type variables cannot be used with isinstance().") def __subclasscheck__(self, cls): raise TypeError("Type variables cannot be used with issubclass().") # Some unconstrained type variables. These are used by the container types. # (These are not for export.) 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. # A useful type variable with constraints. This represents string types. # (This one *is* for export!) AnyStr = TypeVar('AnyStr', bytes, str) def _replace_arg(arg, tvars, args): """An internal helper function: replace arg if it is a type variable found in tvars with corresponding substitution from args or with corresponding substitution sub-tree if arg is a generic type. """ if tvars is None: tvars = [] if hasattr(arg, '_subs_tree'): return arg._subs_tree(tvars, args) if isinstance(arg, TypeVar): for i, tvar in enumerate(tvars): if arg == tvar: return args[i] return arg def _subs_tree(cls, tvars=None, args=None): """An internal helper function: calculate substitution tree for generic cls after replacing its type parameters with substitutions in tvars -> args (if any). Repeat the same following __origin__'s. Return a list of arguments with all possible substitutions performed. Arguments that are generic classes themselves are represented as tuples (so that no new classes are created by this function). For example: _subs_tree(List[Tuple[int, T]][str]) == [(Tuple, int, str)] """ if cls.__origin__ is None: return cls # Make of chain of origins (i.e. cls -> cls.__origin__) current = cls.__origin__ orig_chain = [] while current.__origin__ is not None: orig_chain.append(current) current = current.__origin__ # Replace type variables in __args__ if asked ... tree_args = [] for arg in cls.__args__: tree_args.append(_replace_arg(arg, tvars, args)) # ... then continue replacing down the origin chain. for ocls in orig_chain: new_tree_args = [] for i, arg in enumerate(ocls.__args__): new_tree_args.append(_replace_arg(arg, ocls.__parameters__, tree_args)) tree_args = new_tree_args return tree_args def _remove_dups_flatten(parameters): """An internal helper for Union creation and substitution: flatten Union's among parameters, then remove duplicates and strict subclasses. """ # Flatten out Union[Union[...], ...]. params = [] for p in parameters: if isinstance(p, _Union) and p.__origin__ is Union: 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) # 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 # Weed out subclasses. # E.g. Union[int, Employee, Manager] == Union[int, Employee]. # If object is present it will be sole survivor among proper classes. # Never discard type variables. # (In particular, Union[str, AnyStr] != AnyStr.) all_params = set(params) for t1 in params: if not isinstance(t1, type): continue if any(isinstance(t2, type) and issubclass(t1, t2) for t2 in all_params - {t1} if not (isinstance(t2, GenericMeta) and t2.__origin__ is not None)): all_params.remove(t1) return tuple(t for t in params if t in all_params) def _check_generic(cls, parameters): # Check correct count for parameters of a generic cls (internal helper). if not cls.__parameters__: raise TypeError("%s is not a generic class" % repr(cls)) alen = len(parameters) elen = len(cls.__parameters__) if alen != elen: raise TypeError("Too %s parameters for %s; actual %s, expected %s" % ("many" if alen > elen else "few", repr(cls), alen, elen)) _cleanups = [] def _tp_cache(func): """Internal wrapper caching __getitem__ of generic types with a fallback to original function for non-hashable arguments. """ cached = functools.lru_cache()(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 class _Union(_FinalTypingBase, _root=True): """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] - When two arguments have a subclass relationship, the least derived argument is kept, e.g.:: class Employee: pass class Manager(Employee): pass Union[int, Employee, Manager] == Union[int, Employee] Union[Manager, int, Employee] == Union[int, Employee] Union[Employee, Manager] == Employee - Similar for object:: Union[int, object] == object - You cannot subclass or instantiate a union. - You can use Optional[X] as a shorthand for Union[X, None]. """ __slots__ = ('__parameters__', '__args__', '__origin__', '__tree_hash__') def __new__(cls, parameters=None, origin=None, *args, _root=False): self = super().__new__(cls, parameters, origin, *args, _root=_root) if origin is None: self.__parameters__ = None self.__args__ = None self.__origin__ = None self.__tree_hash__ = hash(frozenset(('Union',))) return self if not isinstance(parameters, tuple): raise TypeError("Expected parameters=<tuple>") if origin is Union: parameters = _remove_dups_flatten(parameters) # It's not a union if there's only one type left. if len(parameters) == 1: return parameters[0] self.__parameters__ = _type_vars(parameters) self.__args__ = parameters self.__origin__ = origin # Pre-calculate the __hash__ on instantiation. # This improves speed for complex substitutions. subs_tree = self._subs_tree() if isinstance(subs_tree, tuple): self.__tree_hash__ = hash(frozenset(subs_tree)) else: self.__tree_hash__ = hash(subs_tree) return self def _eval_type(self, globalns, localns): if self.__args__ is None: return self ev_args = tuple(_eval_type(t, globalns, localns) for t in self.__args__) ev_origin = _eval_type(self.__origin__, globalns, localns) if ev_args == self.__args__ and ev_origin == self.__origin__: # Everything is already evaluated. return self return self.__class__(ev_args, ev_origin, _root=True) def _get_type_vars(self, tvars): if self.__origin__ and self.__parameters__: _get_type_vars(self.__parameters__, tvars) def __repr__(self): if self.__origin__ is None: return super().__repr__() tree = self._subs_tree() if not isinstance(tree, tuple): return repr(tree) return tree[0]._tree_repr(tree) def _tree_repr(self, tree): arg_list = [] for arg in tree[1:]: if not isinstance(arg, tuple): arg_list.append(_type_repr(arg)) else: arg_list.append(arg[0]._tree_repr(arg)) return super().__repr__() + '[%s]' % ', '.join(arg_list) @_tp_cache def __getitem__(self, parameters): if parameters == (): raise TypeError("Cannot take a Union of no types.") if not isinstance(parameters, tuple): parameters = (parameters,) if self.__origin__ is None: msg = "Union[arg, ...]: each arg must be a type." else: msg = "Parameters to generic types must be types." parameters = tuple(_type_check(p, msg) for p in parameters) if self is not Union: _check_generic(self, parameters) return self.__class__(parameters, origin=self, _root=True) def _subs_tree(self, tvars=None, args=None): if self is Union: return Union # Nothing to substitute tree_args = _subs_tree(self, tvars, args) tree_args = _remove_dups_flatten(tree_args) if len(tree_args) == 1: return tree_args[0] # Union of a single type is that type return (Union,) + tree_args def __eq__(self, other): if not isinstance(other, _Union): return self._subs_tree() == other return self.__tree_hash__ == other.__tree_hash__ def __hash__(self): return self.__tree_hash__ def __instancecheck__(self, obj): raise TypeError("Unions cannot be used with isinstance().") def __subclasscheck__(self, cls): raise TypeError("Unions cannot be used with issubclass().") Union = _Union(_root=True) class _Optional(_FinalTypingBase, _root=True): """Optional type. Optional[X] is equivalent to Union[X, None]. """ __slots__ = () @_tp_cache def __getitem__(self, arg): arg = _type_check(arg, "Optional[t] requires a single type.") return Union[arg, type(None)] Optional = _Optional(_root=True) def _gorg(a): """Return the farthest origin of a generic class (internal helper).""" assert isinstance(a, GenericMeta) while a.__origin__ is not None: a = a.__origin__ return a def _geqv(a, b): """Return whether two generic classes are equivalent (internal helper). The intention is to consider generic class X and any of its parameterized forms (X[T], X[int], etc.) as equivalent. However, X is not equivalent to a subclass of X. The relation is reflexive, symmetric and transitive. """ assert isinstance(a, GenericMeta) and isinstance(b, GenericMeta) # Reduce each to its origin. return _gorg(a) is _gorg(b) def _next_in_mro(cls): """Helper for Generic.__new__. Returns the class after the last occurrence of Generic or Generic[...] in cls.__mro__. """ next_in_mro = object # Look for the last occurrence of Generic or Generic[...]. for i, c in enumerate(cls.__mro__[:-1]): if isinstance(c, GenericMeta) and _gorg(c) is Generic: next_in_mro = cls.__mro__[i+1] return next_in_mro def _valid_for_check(cls): """An internal helper to prohibit isinstance([1], List[str]) etc.""" if cls is Generic: raise TypeError("Class %r cannot be used with class " "or instance checks" % cls) if (cls.__origin__ is not None and sys._getframe(3).f_globals['__name__'] not in ['abc', 'functools']): raise TypeError("Parameterized generics cannot be used with class " "or instance checks") def _make_subclasshook(cls): """Construct a __subclasshook__ callable that incorporates the associated __extra__ class in subclass checks performed against cls. """ if isinstance(cls.__extra__, abc.ABCMeta): # The logic mirrors that of ABCMeta.__subclasscheck__. # Registered classes need not be checked here because # cls and its extra share the same _abc_registry. def __extrahook__(subclass): _valid_for_check(cls) res = cls.__extra__.__subclasshook__(subclass) if res is not NotImplemented: return res if cls.__extra__ in subclass.__mro__: return True for scls in cls.__extra__.__subclasses__(): if isinstance(scls, GenericMeta): continue if issubclass(subclass, scls): return True return NotImplemented else: # For non-ABC extras we'll just call issubclass(). def __extrahook__(subclass): _valid_for_check(cls) if cls.__extra__ and issubclass(subclass, cls.__extra__): return True return NotImplemented return __extrahook__ def _no_slots_copy(dct): """Internal helper: copy class __dict__ and clean slots class variables. (They will be re-created if necessary by normal class machinery.) """ dict_copy = dict(dct) if '__slots__' in dict_copy: for slot in dict_copy['__slots__']: dict_copy.pop(slot, None) return dict_copy class GenericMeta(TypingMeta, abc.ABCMeta): """Metaclass for generic types.""" def __new__(cls, name, bases, namespace, tvars=None, args=None, origin=None, extra=None, orig_bases=None): if tvars is not None: # Called from __getitem__() below. assert origin is not None assert all(isinstance(t, TypeVar) for t in tvars), tvars else: # Called from class statement. assert tvars is None, tvars assert args is None, args assert origin is None, origin # Get the full set of tvars from the bases. tvars = _type_vars(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 bases: if base is Generic: raise TypeError("Cannot inherit from plain Generic") if (isinstance(base, GenericMeta) and base.__origin__ is Generic): if gvars is not None: raise TypeError( "Cannot inherit from Generic[...] multiple types.") gvars = base.__parameters__ if gvars is None: gvars = tvars else: tvarset = set(tvars) gvarset = set(gvars) if not tvarset <= gvarset: raise TypeError( "Some type variables (%s) " "are not listed in Generic[%s]" % (", ".join(str(t) for t in tvars if t not in gvarset), ", ".join(str(g) for g in gvars))) tvars = gvars initial_bases = bases if extra is not None and type(extra) is abc.ABCMeta and extra not in bases: bases = (extra,) + bases bases = tuple(_gorg(b) if isinstance(b, GenericMeta) else b for b in bases) # remove bare Generic from bases if there are other generic bases if any(isinstance(b, GenericMeta) and b is not Generic for b in bases): bases = tuple(b for b in bases if b is not Generic) self = super().__new__(cls, name, bases, namespace, _root=True) self.__parameters__ = tvars # Be prepared that GenericMeta will be subclassed by TupleMeta # and CallableMeta, those two allow ..., (), or [] in __args___. self.__args__ = tuple(... if a is _TypingEllipsis else () if a is _TypingEmpty else a for a in args) if args else None self.__origin__ = origin self.__extra__ = extra # Speed hack (https://github.com/python/typing/issues/196). self.__next_in_mro__ = _next_in_mro(self) # Preserve base classes on subclassing (__bases__ are type erased now). if orig_bases is None: self.__orig_bases__ = initial_bases # This allows unparameterized generic collections to be used # with issubclass() and isinstance() in the same way as their # collections.abc counterparts (e.g., isinstance([], Iterable)). if ('__subclasshook__' not in namespace and extra # allow overriding or hasattr(self.__subclasshook__, '__name__') and self.__subclasshook__.__name__ == '__extrahook__'): self.__subclasshook__ = _make_subclasshook(self) if isinstance(extra, abc.ABCMeta): self._abc_registry = extra._abc_registry if origin and hasattr(origin, '__qualname__'): # Fix for Python 3.2. self.__qualname__ = origin.__qualname__ self.__tree_hash__ = hash(self._subs_tree()) if origin else hash((self.__name__,)) return self def _get_type_vars(self, tvars): if self.__origin__ and self.__parameters__: _get_type_vars(self.__parameters__, tvars) def _eval_type(self, globalns, localns): ev_origin = (self.__origin__._eval_type(globalns, localns) if self.__origin__ else None) ev_args = tuple(_eval_type(a, globalns, localns) for a in self.__args__) if self.__args__ else None if ev_origin == self.__origin__ and ev_args == self.__args__: return self return self.__class__(self.__name__, self.__bases__, _no_slots_copy(self.__dict__), tvars=_type_vars(ev_args) if ev_args else None, args=ev_args, origin=ev_origin, extra=self.__extra__, orig_bases=self.__orig_bases__) def __repr__(self): if self.__origin__ is None: return super().__repr__() return self._tree_repr(self._subs_tree()) def _tree_repr(self, tree): arg_list = [] for arg in tree[1:]: if arg == (): arg_list.append('()') elif not isinstance(arg, tuple): arg_list.append(_type_repr(arg)) else: arg_list.append(arg[0]._tree_repr(arg)) return super().__repr__() + '[%s]' % ', '.join(arg_list) def _subs_tree(self, tvars=None, args=None): if self.__origin__ is None: return self tree_args = _subs_tree(self, tvars, args) return (_gorg(self),) + tuple(tree_args) def __eq__(self, other): if not isinstance(other, GenericMeta): return NotImplemented if self.__origin__ is None or other.__origin__ is None: return self is other return self.__tree_hash__ == other.__tree_hash__ def __hash__(self): return self.__tree_hash__ @_tp_cache def __getitem__(self, params): if not isinstance(params, tuple): params = (params,) if not params and not _gorg(self) is Tuple: raise TypeError( "Parameter list to %s[...] cannot be empty" % _qualname(self)) msg = "Parameters to generic types must be types." params = tuple(_type_check(p, msg) for p in params) if self is Generic: # Generic can only be subscripted with unique type variables. if not all(isinstance(p, TypeVar) for p in params): raise TypeError( "Parameters to Generic[...] must all be type variables") if len(set(params)) != len(params): raise TypeError( "Parameters to Generic[...] must all be unique") tvars = params args = params elif self in (Tuple, Callable): tvars = _type_vars(params) args = params elif self is _Protocol: # _Protocol is internal, don't check anything. tvars = params args = params elif self.__origin__ in (Generic, _Protocol): # Can't subscript Generic[...] or _Protocol[...]. raise TypeError("Cannot subscript already-subscripted %s" % repr(self)) else: # Subscripting a regular Generic subclass. _check_generic(self, params) tvars = _type_vars(params) args = params return self.__class__(self.__name__, self.__bases__, _no_slots_copy(self.__dict__), tvars=tvars, args=args, origin=self, extra=self.__extra__, orig_bases=self.__orig_bases__) def __instancecheck__(self, instance): # Since we extend ABC.__subclasscheck__ and # ABC.__instancecheck__ inlines the cache checking done by the # latter, we must extend __instancecheck__ too. For simplicity # we just skip the cache check -- instance checks for generic # classes are supposed to be rare anyways. return issubclass(instance.__class__, self) def __copy__(self): return self.__class__(self.__name__, self.__bases__, _no_slots_copy(self.__dict__), self.__parameters__, self.__args__, self.__origin__, self.__extra__, self.__orig_bases__) # Prevent checks for Generic to crash when defining Generic. Generic = None def _generic_new(base_cls, cls, *args, **kwds): # Assure type is erased on instantiation, # but attempt to store it in __orig_class__ if cls.__origin__ is None: return base_cls.__new__(cls) else: origin = _gorg(cls) obj = base_cls.__new__(origin) try: obj.__orig_class__ = cls except AttributeError: pass obj.__init__(*args, **kwds) return obj class Generic(metaclass=GenericMeta): """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__ = () def __new__(cls, *args, **kwds): if _geqv(cls, Generic): raise TypeError("Type Generic cannot be instantiated; " "it can be used only as a base class") return _generic_new(cls.__next_in_mro__, cls, *args, **kwds) class _TypingEmpty: """Internal placeholder for () or []. Used by TupleMeta and CallableMeta to allow empty list/tuple in specific places, without allowing them to sneak in where prohibited. """ class _TypingEllipsis: """Internal placeholder for ... (ellipsis).""" class TupleMeta(GenericMeta): """Metaclass for Tuple (internal).""" @_tp_cache def __getitem__(self, parameters): if self.__origin__ is not None or not _geqv(self, Tuple): # Normal generic rules apply if this is not the first subscription # or a subscription of a subclass. return super().__getitem__(parameters) if parameters == (): return super().__getitem__((_TypingEmpty,)) if not isinstance(parameters, tuple): parameters = (parameters,) if len(parameters) == 2 and parameters[1] is ...: msg = "Tuple[t, ...]: t must be a type." p = _type_check(parameters[0], msg) return super().__getitem__((p, _TypingEllipsis)) msg = "Tuple[t0, t1, ...]: each t must be a type." parameters = tuple(_type_check(p, msg) for p in parameters) return super().__getitem__(parameters) def __instancecheck__(self, obj): if self.__args__ == None: return isinstance(obj, tuple) raise TypeError("Parameterized Tuple cannot be used " "with isinstance().") def __subclasscheck__(self, cls): if self.__args__ == None: return issubclass(cls, tuple) raise TypeError("Parameterized Tuple cannot be used " "with issubclass().") class Tuple(tuple, extra=tuple, metaclass=TupleMeta): """Tuple type; 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, ...]. """ __slots__ = () def __new__(cls, *args, **kwds): if _geqv(cls, Tuple): raise TypeError("Type Tuple cannot be instantiated; " "use tuple() instead") return _generic_new(tuple, cls, *args, **kwds) class CallableMeta(GenericMeta): """Metaclass for Callable (internal).""" def __repr__(self): if self.__origin__ is None: return super().__repr__() return self._tree_repr(self._subs_tree()) def _tree_repr(self, tree): if _gorg(self) is not Callable: return super()._tree_repr(tree) # For actual Callable (not its subclass) we override # super()._tree_repr() for nice formatting. arg_list = [] for arg in tree[1:]: if not isinstance(arg, tuple): arg_list.append(_type_repr(arg)) else: arg_list.append(arg[0]._tree_repr(arg)) if arg_list[0] == '...': return repr(tree[0]) + '[..., %s]' % arg_list[1] return (repr(tree[0]) + '[[%s], %s]' % (', '.join(arg_list[:-1]), arg_list[-1])) def __getitem__(self, parameters): """A thin wrapper around __getitem_inner__ to provide the latter with hashable arguments to improve speed. """ if self.__origin__ is not None or not _geqv(self, Callable): return super().__getitem__(parameters) if not isinstance(parameters, tuple) or len(parameters) != 2: raise TypeError("Callable must be used as " "Callable[[arg, ...], result].") args, result = parameters if args is Ellipsis: parameters = (Ellipsis, result) else: if not isinstance(args, list): raise TypeError("Callable[args, result]: args must be a list." " Got %.100r." % (args,)) parameters = (tuple(args), result) return self.__getitem_inner__(parameters) @_tp_cache def __getitem_inner__(self, parameters): args, result = parameters msg = "Callable[args, result]: result must be a type." result = _type_check(result, msg) if args is Ellipsis: return super().__getitem__((_TypingEllipsis, result)) msg = "Callable[[arg, ...], result]: each arg must be a type." args = tuple(_type_check(arg, msg) for arg in args) parameters = args + (result,) return super().__getitem__(parameters) class Callable(extra=collections_abc.Callable, metaclass = CallableMeta): """Callable type; Callable[[int], str] is a function of (int) -> 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 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. """ __slots__ = () def __new__(cls, *args, **kwds): if _geqv(cls, Callable): raise TypeError("Type Callable cannot be instantiated; " "use a non-abstract subclass instead") return _generic_new(cls.__next_in_mro__, cls, *args, **kwds) class _ClassVar(_FinalTypingBase, _root=True): """Special type construct to mark class variables. An annotation wrapped in ClassVar indicates that a given attribute is intended to be used as a class variable and should not be set on instances of that class. Usage:: class Starship: stats: ClassVar[Dict[str, int]] = {} # class variable damage: int = 10 # instance variable ClassVar accepts only types and cannot be further subscribed. Note that ClassVar is not a class itself, and should not be used with isinstance() or issubclass(). """ __slots__ = ('__type__',) def __init__(self, tp=None, **kwds): self.__type__ = tp def __getitem__(self, item): cls = type(self) if self.__type__ is None: return cls(_type_check(item, '{} accepts only single type.'.format(cls.__name__[1:])), _root=True) raise TypeError('{} cannot be further subscripted' .format(cls.__name__[1:])) def _eval_type(self, globalns, localns): new_tp = _eval_type(self.__type__, globalns, localns) if new_tp == self.__type__: return self return type(self)(new_tp, _root=True) def __repr__(self): r = super().__repr__() if self.__type__ is not None: r += '[{}]'.format(_type_repr(self.__type__)) return r def __hash__(self): return hash((type(self).__name__, self.__type__)) def __eq__(self, other): if not isinstance(other, _ClassVar): return NotImplemented if self.__type__ is not None: return self.__type__ == other.__type__ return self is other ClassVar = _ClassVar(_root=True) def cast(typ, val): """Cast a value to a type. 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 _get_defaults(func): """Internal helper to extract the default arguments, by name.""" try: code = func.__code__ except AttributeError: # Some built-in functions don't have __code__, __defaults__, etc. return {} pos_count = code.co_argcount arg_names = code.co_varnames arg_names = arg_names[:pos_count] defaults = func.__defaults__ or () kwdefaults = func.__kwdefaults__ res = dict(kwdefaults) if kwdefaults else {} pos_offset = pos_count - len(defaults) for name, value in zip(arg_names[pos_offset:], defaults): assert name not in res res[name] = value return res def get_type_hints(obj, globalns=None, localns=None): """Return type hints for an object. This is often the same as obj.__annotations__, but it handles forward references encoded as string literals, and if necessary adds Optional[t] if a default value equal to None is set. The argument may be a module, class, method, or function. The annotations are returned as a dictionary. 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, and these are also used as the locals. If the object does not appear to have globals, an exception is raised. - 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 {} if globalns is None: globalns = getattr(obj, '__globals__', {}) if localns is None: localns = globalns elif localns is None: localns = globalns # Classes require a special treatment. if isinstance(obj, type): hints = {} for base in reversed(obj.__mro__): ann = base.__dict__.get('__annotations__', {}) for name, value in ann.items(): if value is None: value = type(None) if isinstance(value, str): value = _ForwardRef(value) value = _eval_type(value, globalns, localns) hints[name] = value return hints hints = getattr(obj, '__annotations__', None) if hints is None: # Return empty annotations for something that _could_ have them. if (isinstance(obj, types.FunctionType) or isinstance(obj, types.BuiltinFunctionType) or isinstance(obj, types.MethodType) or isinstance(obj, types.ModuleType)): return {} else: raise TypeError('{!r} is not a module, class, method, ' 'or function.'.format(obj)) defaults = _get_defaults(obj) hints = dict(hints) for name, value in hints.items(): if value is None: value = type(None) if isinstance(value, str): value = _ForwardRef(value) value = _eval_type(value, globalns, localns) if name in defaults and defaults[name] is None: value = Optional[value] hints[name] = value return hints 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): arg_attrs = arg.__dict__.copy() for attr, val in arg.__dict__.items(): if val in arg.__bases__: arg_attrs.pop(attr) for obj in arg_attrs.values(): if isinstance(obj, types.FunctionType): obj.__no_type_check__ = True if isinstance(obj, type): no_type_check(obj) try: arg.__no_type_check__ = True except TypeError: # built-in classes pass return arg def no_type_check_decorator(decorator): """Decorator to give another decorator the @no_type_check effect. This wraps the decorator with something that wraps the decorated function in @no_type_check. """ @functools.wraps(decorator) def wrapped_decorator(*args, **kwds): func = decorator(*args, **kwds) func = no_type_check(func) return func return wrapped_decorator def _overload_dummy(*args, **kwds): """Helper for @overload to raise when called.""" raise NotImplementedError( "You should not call an overloaded function. " "A series of @overload-decorated functions " "outside a stub module should always be followed " "by an implementation that is not @overload-ed.") 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. For example: @overload def utf8(value: None) -> None: ... @overload def utf8(value: bytes) -> bytes: ... @overload def utf8(value: str) -> bytes: ... def utf8(value): # implementation goes here """ return _overload_dummy class _ProtocolMeta(GenericMeta): """Internal metaclass for _Protocol. This exists so _Protocol classes can be generic without deriving from Generic. """ def __instancecheck__(self, obj): if _Protocol not in self.__bases__: return super().__instancecheck__(obj) raise TypeError("Protocols cannot be used with isinstance().") def __subclasscheck__(self, cls): if not self._is_protocol: # No structural checks since this isn't a protocol. return NotImplemented if self is _Protocol: # Every class is a subclass of the empty protocol. return True # Find all attributes defined in the protocol. attrs = self._get_protocol_attrs() for attr in attrs: if not any(attr in d.__dict__ for d in cls.__mro__): return False return True def _get_protocol_attrs(self): # Get all Protocol base classes. protocol_bases = [] for c in self.__mro__: if getattr(c, '_is_protocol', False) and c.__name__ != '_Protocol': protocol_bases.append(c) # Get attributes included in protocol. attrs = set() for base in protocol_bases: for attr in base.__dict__.keys(): # Include attributes not defined in any non-protocol bases. for c in self.__mro__: if (c is not base and attr in c.__dict__ and not getattr(c, '_is_protocol', False)): break else: if (not attr.startswith('_abc_') and attr != '__abstractmethods__' and attr != '__annotations__' and attr != '__weakref__' and attr != '_is_protocol' and attr != '__dict__' and attr != '__args__' and attr != '__slots__' and attr != '_get_protocol_attrs' and attr != '__next_in_mro__' and attr != '__parameters__' and attr != '__origin__' and attr != '__orig_bases__' and attr != '__extra__' and attr != '__tree_hash__' and attr != '__module__'): attrs.add(attr) return attrs class _Protocol(metaclass=_ProtocolMeta): """Internal base class for protocol classes. This implements a simple-minded structural issubclass check (similar but more general than the one-offs in collections.abc such as Hashable). """ __slots__ = () _is_protocol = True # Various ABCs mimicking those in collections.abc. # A few are simply re-exported for completeness. Hashable = collections_abc.Hashable # Not generic. if hasattr(collections_abc, 'Awaitable'): class Awaitable(Generic[T_co], extra=collections_abc.Awaitable): __slots__ = () __all__.append('Awaitable') if hasattr(collections_abc, 'Coroutine'): class Coroutine(Awaitable[V_co], Generic[T_co, T_contra, V_co], extra=collections_abc.Coroutine): __slots__ = () __all__.append('Coroutine') if hasattr(collections_abc, 'AsyncIterable'): class AsyncIterable(Generic[T_co], extra=collections_abc.AsyncIterable): __slots__ = () class AsyncIterator(AsyncIterable[T_co], extra=collections_abc.AsyncIterator): __slots__ = () __all__.append('AsyncIterable') __all__.append('AsyncIterator') class Iterable(Generic[T_co], extra=collections_abc.Iterable): __slots__ = () class Iterator(Iterable[T_co], extra=collections_abc.Iterator): __slots__ = () class SupportsInt(_Protocol): __slots__ = () @abstractmethod def __int__(self) -> int: pass class SupportsFloat(_Protocol): __slots__ = () @abstractmethod def __float__(self) -> float: pass class SupportsComplex(_Protocol): __slots__ = () @abstractmethod def __complex__(self) -> complex: pass class SupportsBytes(_Protocol): __slots__ = () @abstractmethod def __bytes__(self) -> bytes: pass class SupportsAbs(_Protocol[T_co]): __slots__ = () @abstractmethod def __abs__(self) -> T_co: pass class SupportsRound(_Protocol[T_co]): __slots__ = () @abstractmethod def __round__(self, ndigits: int = 0) -> T_co: pass if hasattr(collections_abc, 'Reversible'): class Reversible(Iterable[T_co], extra=collections_abc.Reversible): __slots__ = () else: class Reversible(_Protocol[T_co]): __slots__ = () @abstractmethod def __reversed__(self) -> 'Iterator[T_co]': pass Sized = collections_abc.Sized # Not generic. class Container(Generic[T_co], extra=collections_abc.Container): __slots__ = () if hasattr(collections_abc, 'Collection'): class Collection(Sized, Iterable[T_co], Container[T_co], extra=collections_abc.Collection): __slots__ = () __all__.append('Collection') # Callable was defined earlier. if hasattr(collections_abc, 'Collection'): class AbstractSet(Collection[T_co], extra=collections_abc.Set): __slots__ = () else: class AbstractSet(Sized, Iterable[T_co], Container[T_co], extra=collections_abc.Set): __slots__ = () class MutableSet(AbstractSet[T], extra=collections_abc.MutableSet): __slots__ = () # NOTE: It is only covariant in the value type. if hasattr(collections_abc, 'Collection'): class Mapping(Collection[KT], Generic[KT, VT_co], extra=collections_abc.Mapping): __slots__ = () else: class Mapping(Sized, Iterable[KT], Container[KT], Generic[KT, VT_co], extra=collections_abc.Mapping): __slots__ = () class MutableMapping(Mapping[KT, VT], extra=collections_abc.MutableMapping): __slots__ = () if hasattr(collections_abc, 'Reversible'): if hasattr(collections_abc, 'Collection'): class Sequence(Reversible[T_co], Collection[T_co], extra=collections_abc.Sequence): __slots__ = () else: class Sequence(Sized, Reversible[T_co], Container[T_co], extra=collections_abc.Sequence): __slots__ = () else: class Sequence(Sized, Iterable[T_co], Container[T_co], extra=collections_abc.Sequence): __slots__ = () class MutableSequence(Sequence[T], extra=collections_abc.MutableSequence): __slots__ = () class ByteString(Sequence[int], extra=collections_abc.ByteString): __slots__ = () class List(list, MutableSequence[T], extra=list): __slots__ = () def __new__(cls, *args, **kwds): if _geqv(cls, List): raise TypeError("Type List cannot be instantiated; " "use list() instead") return _generic_new(list, cls, *args, **kwds) class Set(set, MutableSet[T], extra=set): __slots__ = () def __new__(cls, *args, **kwds): if _geqv(cls, Set): raise TypeError("Type Set cannot be instantiated; " "use set() instead") return _generic_new(set, cls, *args, **kwds) class FrozenSet(frozenset, AbstractSet[T_co], extra=frozenset): __slots__ = () def __new__(cls, *args, **kwds): if _geqv(cls, FrozenSet): raise TypeError("Type FrozenSet cannot be instantiated; " "use frozenset() instead") return _generic_new(frozenset, cls, *args, **kwds) class MappingView(Sized, Iterable[T_co], extra=collections_abc.MappingView): __slots__ = () class KeysView(MappingView[KT], AbstractSet[KT], extra=collections_abc.KeysView): __slots__ = () class ItemsView(MappingView[Tuple[KT, VT_co]], AbstractSet[Tuple[KT, VT_co]], Generic[KT, VT_co], extra=collections_abc.ItemsView): __slots__ = () class ValuesView(MappingView[VT_co], extra=collections_abc.ValuesView): __slots__ = () if hasattr(contextlib, 'AbstractContextManager'): class ContextManager(Generic[T_co], extra=contextlib.AbstractContextManager): __slots__ = () __all__.append('ContextManager') class Dict(dict, MutableMapping[KT, VT], extra=dict): __slots__ = () def __new__(cls, *args, **kwds): if _geqv(cls, Dict): raise TypeError("Type Dict cannot be instantiated; " "use dict() instead") return _generic_new(dict, cls, *args, **kwds) class DefaultDict(collections.defaultdict, MutableMapping[KT, VT], extra=collections.defaultdict): __slots__ = () def __new__(cls, *args, **kwds): if _geqv(cls, DefaultDict): raise TypeError("Type DefaultDict cannot be instantiated; " "use collections.defaultdict() instead") return _generic_new(collections.defaultdict, cls, *args, **kwds) # Determine what base class to use for Generator. if hasattr(collections_abc, 'Generator'): # Sufficiently recent versions of 3.5 have a Generator ABC. _G_base = collections_abc.Generator else: # Fall back on the exact type. _G_base = types.GeneratorType class Generator(Iterator[T_co], Generic[T_co, T_contra, V_co], extra=_G_base): __slots__ = () def __new__(cls, *args, **kwds): if _geqv(cls, Generator): raise TypeError("Type Generator cannot be instantiated; " "create a subclass instead") return _generic_new(_G_base, cls, *args, **kwds) # Internal type variable used for Type[]. CT_co = TypeVar('CT_co', covariant=True, bound=type) # This is not a real generic class. Don't use outside annotations. class Type(Generic[CT_co], extra=type): """A special construct usable 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:: U = TypeVar('U', bound=User) def new_user(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. """ __slots__ = () def _make_nmtuple(name, types): msg = "NamedTuple('Name', [(f0, t0), (f1, t1), ...]); each t must be a type" types = [(n, _type_check(t, msg)) for n, t in types] nm_tpl = collections.namedtuple(name, [n for n, t in types]) nm_tpl._field_types = dict(types) try: nm_tpl.__module__ = sys._getframe(2).f_globals.get('__name__', '__main__') except (AttributeError, ValueError): pass return nm_tpl _PY36 = sys.version_info[:2] >= (3, 6) class NamedTupleMeta(type): def __new__(cls, typename, bases, ns): if ns.get('_root', False): return super().__new__(cls, typename, bases, ns) if not _PY36: raise TypeError("Class syntax for NamedTuple is only supported" " in Python 3.6+") types = ns.get('__annotations__', {}) return _make_nmtuple(typename, types.items()) class NamedTuple(metaclass=NamedTupleMeta): """Typed version of namedtuple. Usage in Python versions >= 3.6:: class Employee(NamedTuple): name: str id: int This is equivalent to:: Employee = collections.namedtuple('Employee', ['name', 'id']) The resulting class has one extra attribute: _field_types, giving a dict mapping field names to types. (The field names are in the _fields attribute, which is part of the namedtuple API.) Alternative equivalent keyword syntax is also accepted:: Employee = NamedTuple('Employee', name=str, id=int) In Python versions <= 3.5 use:: Employee = NamedTuple('Employee', [('name', str), ('id', int)]) """ _root = True def __new__(self, typename, fields=None, **kwargs): if kwargs and not _PY36: raise TypeError("Keyword syntax for NamedTuple is only supported" " in Python 3.6+") if fields is None: fields = kwargs.items() elif kwargs: raise TypeError("Either list of fields or keywords" " can be provided to NamedTuple, not both") return _make_nmtuple(typename, fields) def NewType(name, tp): """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 function 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 """ def new_type(x): return x new_type.__name__ = name new_type.__supertype__ = tp return new_type # 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__ = () @abstractproperty def mode(self) -> str: pass @abstractproperty def name(self) -> str: pass @abstractmethod def close(self) -> None: pass @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__ = () @abstractproperty def buffer(self) -> BinaryIO: pass @abstractproperty def encoding(self) -> str: pass @abstractproperty def errors(self) -> Optional[str]: pass @abstractproperty def line_buffering(self) -> bool: pass @abstractproperty def newlines(self) -> Any: pass @abstractmethod def __enter__(self) -> 'TextIO': pass class io: """Wrapper namespace for IO generic classes.""" __all__ = ['IO', 'TextIO', 'BinaryIO'] IO = IO TextIO = TextIO BinaryIO = BinaryIO io.__name__ = __name__ + '.io' sys.modules[io.__name__] = io Pattern = _TypeAlias('Pattern', AnyStr, type(stdlib_re.compile('')), lambda p: p.pattern) Match = _TypeAlias('Match', AnyStr, type(stdlib_re.match('', '')), lambda m: m.re.pattern) class re: """Wrapper namespace for re type aliases.""" __all__ = ['Pattern', 'Match'] Pattern = Pattern Match = Match re.__name__ = __name__ + '.re' sys.modules[re.__name__] = re