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- """Defines experimental extensions to the standard "typing" module that are
- supported by the mypy typechecker.
- Example usage:
- from mypy_extensions import TypedDict
- """
- from typing import Any
- import sys
- # _type_check is NOT a part of public typing API, it is used here only to mimic
- # the (convenient) behavior of types provided by typing module.
- from typing import _type_check # type: ignore
- def _check_fails(cls, other):
- try:
- if sys._getframe(1).f_globals['__name__'] not in ['abc', 'functools', 'typing']:
- # Typed dicts are only for static structural subtyping.
- raise TypeError('TypedDict does not support instance and class checks')
- except (AttributeError, ValueError):
- pass
- return False
- def _dict_new(cls, *args, **kwargs):
- return dict(*args, **kwargs)
- def _typeddict_new(cls, _typename, _fields=None, **kwargs):
- total = kwargs.pop('total', True)
- if _fields is None:
- _fields = kwargs
- elif kwargs:
- raise TypeError("TypedDict takes either a dict or keyword arguments,"
- " but not both")
- ns = {'__annotations__': dict(_fields), '__total__': total}
- try:
- # Setting correct module is necessary to make typed dict classes pickleable.
- ns['__module__'] = sys._getframe(1).f_globals.get('__name__', '__main__')
- except (AttributeError, ValueError):
- pass
- return _TypedDictMeta(_typename, (), ns)
- class _TypedDictMeta(type):
- def __new__(cls, name, bases, ns, total=True):
- # Create new typed dict class object.
- # This method is called directly when TypedDict is subclassed,
- # or via _typeddict_new when TypedDict is instantiated. This way
- # TypedDict supports all three syntaxes described in its docstring.
- # Subclasses and instances of TypedDict return actual dictionaries
- # via _dict_new.
- ns['__new__'] = _typeddict_new if name == 'TypedDict' else _dict_new
- tp_dict = super(_TypedDictMeta, cls).__new__(cls, name, (dict,), ns)
- anns = ns.get('__annotations__', {})
- msg = "TypedDict('Name', {f0: t0, f1: t1, ...}); each t must be a type"
- anns = {n: _type_check(tp, msg) for n, tp in anns.items()}
- for base in bases:
- anns.update(base.__dict__.get('__annotations__', {}))
- tp_dict.__annotations__ = anns
- if not hasattr(tp_dict, '__total__'):
- tp_dict.__total__ = total
- return tp_dict
- __instancecheck__ = __subclasscheck__ = _check_fails
- TypedDict = _TypedDictMeta('TypedDict', (dict,), {})
- TypedDict.__module__ = __name__
- TypedDict.__doc__ = \
- """A simple typed name space. At runtime it is equivalent to a plain dict.
- TypedDict creates a dictionary type that expects all of its
- instances to have a certain set of keys, with each key
- associated with a value of a consistent type. This expectation
- is not checked at runtime but is only enforced by typecheckers.
- Usage::
- Point2D = TypedDict('Point2D', {'x': int, 'y': int, 'label': str})
- a: Point2D = {'x': 1, 'y': 2, 'label': 'good'} # OK
- b: Point2D = {'z': 3, 'label': 'bad'} # Fails type check
- assert Point2D(x=1, y=2, label='first') == dict(x=1, y=2, label='first')
- The type info could be accessed via Point2D.__annotations__. TypedDict
- supports two additional equivalent forms::
- Point2D = TypedDict('Point2D', x=int, y=int, label=str)
- class Point2D(TypedDict):
- x: int
- y: int
- label: str
- The latter syntax is only supported in Python 3.6+, while two other
- syntax forms work for 3.2+
- """
- # Argument constructors for making more-detailed Callables. These all just
- # return their type argument, to make them complete noops in terms of the
- # `typing` module.
- def Arg(type=Any, name=None):
- """A normal positional argument"""
- return type
- def DefaultArg(type=Any, name=None):
- """A positional argument with a default value"""
- return type
- def NamedArg(type=Any, name=None):
- """A keyword-only argument"""
- return type
- def DefaultNamedArg(type=Any, name=None):
- """A keyword-only argument with a default value"""
- return type
- def VarArg(type=Any):
- """A *args-style variadic positional argument"""
- return type
- def KwArg(type=Any):
- """A **kwargs-style variadic keyword argument"""
- return type
- # Return type that indicates a function does not return
- class NoReturn: pass
- def trait(cls):
- return cls
- def mypyc_attr(*attrs, **kwattrs):
- return lambda x: x
- # TODO: We may want to try to properly apply this to any type
- # variables left over...
- class _FlexibleAliasClsApplied:
- def __init__(self, val):
- self.val = val
- def __getitem__(self, args):
- return self.val
- class _FlexibleAliasCls:
- def __getitem__(self, args):
- return _FlexibleAliasClsApplied(args[-1])
- FlexibleAlias = _FlexibleAliasCls()
- class _NativeIntMeta(type):
- def __instancecheck__(cls, inst):
- return isinstance(inst, int)
- _sentinel = object()
- class i64(metaclass=_NativeIntMeta):
- def __new__(cls, x=0, base=_sentinel):
- if base is not _sentinel:
- return int(x, base)
- return int(x)
- class i32(metaclass=_NativeIntMeta):
- def __new__(cls, x=0, base=_sentinel):
- if base is not _sentinel:
- return int(x, base)
- return int(x)
- class i16(metaclass=_NativeIntMeta):
- def __new__(cls, x=0, base=_sentinel):
- if base is not _sentinel:
- return int(x, base)
- return int(x)
- class u8(metaclass=_NativeIntMeta):
- def __new__(cls, x=0, base=_sentinel):
- if base is not _sentinel:
- return int(x, base)
- return int(x)
- for _int_type in i64, i32, i16, u8:
- _int_type.__doc__ = \
- """A native fixed-width integer type when used with mypyc.
- In code not compiled with mypyc, behaves like the 'int' type in these
- runtime contexts:
- * {name}(x[, base=n]) converts a number or string to 'int'
- * isinstance(x, {name}) is the same as isinstance(x, int)
- """.format(name=_int_type.__name__)
- del _int_type
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