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GeezerVison is showing github.com — python-typing/python2/typing.py at master · alvistack/python-typing Expand file tree/ Copy pathtyping.pyMore file actions 2550 lines (1991 loc) · 82.5 KB / Copy pathtyping.pyFile metadata and controls2550 lines (1991 loc) · 82.5 KB 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 from __future__ import absolute_import, unicode_literals import abc from abc import abstractmethod, abstractproperty import collections import functools import re as stdlib_re # Avoid confusion with the re we export. import sys import types import copy 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', 'Final', 'Generic', 'Literal', 'Optional', 'Protocol', 'Tuple', 'Type', 'TypeVar', 'Union', # ABCs (from collections.abc). 'AbstractSet', # collections.abc.Set. 'GenericMeta', # subclass of abc.ABCMeta and a metaclass # for 'Generic' and ABCs below. 'ByteString', 'Container', 'ContextManager', 'Hashable', 'ItemsView', 'Iterable', 'Iterator', 'KeysView', 'Mapping', 'MappingView', 'MutableMapping', 'MutableSequence', 'MutableSet', 'Sequence', 'Sized', 'ValuesView', # Structural checks, a.k.a. protocols. 'Reversible', 'SupportsAbs', 'SupportsComplex', 'SupportsFloat', 'SupportsIndex', 'SupportsInt', # Concrete collection types. 'Counter', 'Deque', 'Dict', 'DefaultDict', 'List', 'Set', 'FrozenSet', 'NamedTuple', # Not really a type. 'TypedDict', # Not really a type. 'Generator', # One-off things. 'AnyStr', 'cast', 'final', '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 _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): whitelist = ('_TypeAlias', '_ForwardRef', '_TypingBase', '_FinalTypingBase') if nm.startswith('_') and nm not in whitelist: nm = nm[1:] return nm class TypingMeta(type): """Metaclass for most types defined in typing module (not a part of public API). 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): return super(TypingMeta, cls).__new__(cls, str(name), bases, namespace) @classmethod def assert_no_subclassing(cls, bases): for base in bases: if isinstance(base, cls): raise TypeError("Cannot subclass %s" % (', '.join(map(_type_repr, bases)) or '()')) 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(object): """Internal indicator of special typing constructs.""" __metaclass__ = TypingMeta __slots__ = ('__weakref__',) 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(_TypingBase, cls).__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): """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, **kwds): self = super(_FinalTypingBase, cls).__new__(cls, *args, **kwds) if '_root' in kwds and kwds['_root'] is True: return self raise TypeError("Cannot instantiate %r" % cls) def __reduce__(self): return _trim_name(type(self).__name__) class _ForwardRef(_TypingBase): """Internal wrapper to hold a forward reference.""" __slots__ = ('__forward_arg__', '__forward_code__', '__forward_evaluated__', '__forward_value__') def __init__(self, arg): super(_ForwardRef, self).__init__(arg) if not isinstance(arg, basestring): 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): """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, basestring), 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, basestring): 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 arg._gorg 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__ == '__builtin__': return _qualname(obj) return '%s.%s' % (obj.__module__, _qualname(obj)) if obj is Ellipsis: return '...' if isinstance(obj, types.FunctionType): return obj.__name__ return repr(obj) class ClassVarMeta(TypingMeta): """Metaclass for _ClassVar""" def __new__(cls, name, bases, namespace): cls.assert_no_subclassing(bases) self = super(ClassVarMeta, cls).__new__(cls, name, bases, namespace) return self class _ClassVar(_FinalTypingBase): """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 = {} # type: ClassVar[Dict[str, int]] # class variable damage = 10 # type: int # 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(). """ __metaclass__ = ClassVarMeta __slots__ = ('__type__',) def __init__(self, tp=None, _root=False): self.__type__ = tp def __getitem__(self, item): cls = type(self) if self.__type__ is None: return cls(_type_check(item, '{} accepts only types.'.format(cls.__name__[1:])), _root=True) raise TypeError('{} cannot be further subscripted' .format(cls.__name__[1:])) def _eval_type(self, globalns, localns): return type(self)(_eval_type(self.__type__, globalns, localns), _root=True) def __repr__(self): r = super(_ClassVar, self).__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) class _FinalMeta(TypingMeta): """Metaclass for _Final""" def __new__(cls, name, bases, namespace): cls.assert_no_subclassing(bases) self = super(_FinalMeta, cls).__new__(cls, name, bases, namespace) return self class _Final(_FinalTypingBase): """A special typing construct to indicate that a 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. """ __metaclass__ = _FinalMeta __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(_Final, self).__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, _Final): return NotImplemented if self.__type__ is not None: return self.__type__ == other.__type__ return self is other Final = _Final(_root=True) def final(f): """This decorator can be used 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. """ return f class _LiteralMeta(TypingMeta): """Metaclass for _Literal""" def __new__(cls, name, bases, namespace): cls.assert_no_subclassing(bases) self = super(_LiteralMeta, cls).__new__(cls, name, bases, namespace) return self class _Literal(_FinalTypingBase): """A type that can be used to indicate to type checkers that the corresponding value has a value literally equivalent to the provided parameter. For example: var: Literal[4] = 4 The type checker understands that 'var' is literally equal to the value 4 and no other value. Literal[...] cannot be subclassed. There is no runtime checking verifying that the parameter is actually a value instead of a type. """ __metaclass__ = _LiteralMeta __slots__ = ('__values__',) def __init__(self, values=None, **kwds): self.__values__ = values def __getitem__(self, item): cls = type(self) if self.__values__ is None: if not isinstance(item, tuple): item = (item,) return cls(values=item, _root=True) raise TypeError('{} cannot be further subscripted' .format(cls.__name__[1:])) def _eval_type(self, globalns, localns): return self def __repr__(self): r = super(_Literal, self).__repr__() if self.__values__ is not None: r += '[{}]'.format(', '.join(map(_type_repr, self.__values__))) return r def __hash__(self): return hash((type(self).__name__, self.__values__)) def __eq__(self, other): if not isinstance(other, _Literal): return NotImplemented if self.__values__ is not None: return self.__values__ == other.__values__ return self is other Literal = _Literal(_root=True) class AnyMeta(TypingMeta): """Metaclass for Any.""" def __new__(cls, name, bases, namespace): cls.assert_no_subclassing(bases) self = super(AnyMeta, cls).__new__(cls, name, bases, namespace) return self class _Any(_FinalTypingBase): """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. """ __metaclass__ = AnyMeta __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 NoReturnMeta(TypingMeta): """Metaclass for NoReturn.""" def __new__(cls, name, bases, namespace): cls.assert_no_subclassing(bases) self = super(NoReturnMeta, cls).__new__(cls, name, bases, namespace) return self class _NoReturn(_FinalTypingBase): """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. """ __metaclass__ = NoReturnMeta __slots__ = () def __instancecheck__(self, obj): raise TypeError("NoReturn cannot be used with isinstance().") def __subclasscheck__(self, cls): raise TypeError("NoReturn cannot be used with issubclass().") NoReturn = _NoReturn(_root=True) class TypeVarMeta(TypingMeta): def __new__(cls, name, bases, namespace): cls.assert_no_subclassing(bases) return super(TypeVarMeta, cls).__new__(cls, name, bases, namespace) class TypeVar(_TypingBase): """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) """ __metaclass__ = TypeVarMeta __slots__ = ('__name__', '__bound__', '__constraints__', '__covariant__', '__contravariant__') def __init__(self, name, *constraints, **kwargs): super(TypeVar, self).__init__(name, *constraints, **kwargs) bound = kwargs.get('bound', None) covariant = kwargs.get('covariant', False) contravariant = kwargs.get('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 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, unicode) 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') and isinstance(arg, (GenericMeta, _TypingBase)): return arg._subs_tree(tvars, args) if isinstance(arg, TypeVar): for i, tvar in enumerate(tvars): if arg == tvar: return args[i] return arg # 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; # * __args__ is a tuple of all arguments used in subscripting, # e.g., Dict[T, int].__args__ == (T, int). 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 arg in 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): maxsize = 128 cache = {} _cleanups.append(cache.clear) @functools.wraps(func) def inner(*args): key = args try: return cache[key] except TypeError: # Assume it's an unhashable argument. return func(*args) except KeyError: value = func(*args) if len(cache) >= maxsize: # If the cache grows too much, just start over. cache.clear() cache[key] = value return value return inner class UnionMeta(TypingMeta): """Metaclass for Union.""" def __new__(cls, name, bases, namespace): cls.assert_no_subclassing(bases) return super(UnionMeta, cls).__new__(cls, name, bases, namespace) class _Union(_FinalTypingBase): """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]. """ __metaclass__ = UnionMeta __slots__ = ('__parameters__', '__args__', '__origin__', '__tree_hash__') def __new__(cls, parameters=None, origin=None, *args, **kwds): self = super(_Union, cls).__new__(cls, parameters, origin, *args, **kwds) 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): |
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