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from collections import OrderedDict
from typing import Optional, Any
class ClsDict(OrderedDict):
"""
ClsDict is a dict that accepts (only) types as keys and will return its
values depending on instance checks rather than equality checks.
"""
def __new__(cls, *args, **kwargs):
"""
Construct a new instance of ``ClsDict``.
:param args: a dict.
:param kwargs: any kwargs that ``dict`` accepts.
:return: a ``ClsDict``.
"""
from typish.functions._is_type_annotation import is_type_annotation
if len(args) > 1:
raise TypeError('TypeDict accepts only one positional argument, '
'which must be a dict.')
if args and not isinstance(args[0], dict):
raise TypeError('TypeDict accepts only a dict as positional '
'argument.')
if not all([is_type_annotation(key) for key in args[0]]):
raise TypeError('The given dict must only hold types as keys.')
return super().__new__(cls, args[0], **kwargs)
def __getitem__(self, item: Any) -> Any:
"""
Return the value of the first encounter of a key for which
``is_instance(item, key)`` holds ``True``.
:param item: any item.
:return: the value of which the type corresponds with item.
"""
from typish.functions._get_type import get_type
from typish.functions._subclass_of import subclass_of
item_type = get_type(item, use_union=True)
for key, value in self.items():
if subclass_of(item_type, key):
return value
raise KeyError('No match for {}'.format(item))
def get(self, item: Any, default: Any = None) -> Optional[Any]:
try:
return self.__getitem__(item)
except KeyError:
return default
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