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from abc import abstractmethod
from typing import TypeVar, Callable, Any
CAPTURE_EXCEPTIONS = (Exception, )
_ValueType = TypeVar('_ValueType')
def _to_exception(exception) -> Callable[[Any], Exception]:
"""
Overview:
Convert exception to callable exception.
Arguments:
- exception (:obj:`Exception`): The exception to be converted.
"""
if hasattr(exception, '__call__'):
return exception
elif isinstance(exception, Exception):
return lambda v: exception
elif isinstance(exception, str):
return lambda v: ValueError(exception)
else:
raise TypeError(
'Unknown type of exception, func, exception or str expected but {actual} found.'.format(
actual=repr(type(exception).__name__)
)
)
def _to_loader(value) -> 'ILoaderClass':
"""
Overview:
Convert value to loader.
Arguments:
- value (:obj:`Any`): The value to be converted.
"""
if isinstance(value, ILoaderClass):
return value
elif isinstance(value, tuple):
if len(value) == 2:
_predict, _exception = value
_load = None
elif len(value) == 3:
_predict, _load, _exception = value
else:
raise ValueError('Tuple\'s length should be 2 or 3, but {actual} found.'.format(actual=repr(len(value))))
_exception = _to_exception(_exception)
def _load_tuple(value_):
if not _predict(value_):
raise _exception(value_)
return (_load or (lambda v: v))(value_)
return _to_loader(_load_tuple)
elif isinstance(value, type):
def _load_type(value_):
if not isinstance(value_, value):
raise TypeError(
'type not match, {expect} expected but {actual} found'.format(
expect=repr(value.__name__), actual=repr(type(value_).__name__)
)
)
return value_
return _to_loader(_load_type)
elif hasattr(value, '__call__'):
class _Loader(ILoaderClass):
def _load(self, value_):
return value(value_)
return _Loader()
elif isinstance(value, bool):
return _to_loader((lambda v: value, ValueError('assertion false')))
elif value is None:
return _to_loader(
(
lambda v: v is None, lambda v:
TypeError('type not match, none expected but {actual} found'.format(actual=repr(type(v).__name__)))
)
)
else:
return _to_loader(lambda v: value)
Loader = _to_loader
def _reset_exception(loader, eg: Callable[[Any, Exception], Exception]):
"""
Overview:
Reset exception of loader.
"""
loader = Loader(loader)
def _load(value):
try:
return loader(value)
except CAPTURE_EXCEPTIONS as err:
raise eg(value, err)
return Loader(_load)
class ILoaderClass:
"""
Overview:
Base class of loader.
Interfaces:
``__init__``, ``_load``, ``load``, ``check``, ``__call__``, ``__and__``, ``__or__``, ``__rshift__``
"""
@abstractmethod
def _load(self, value: _ValueType) -> _ValueType:
"""
Overview:
Load the value.
Arguments:
- value (:obj:`_ValueType`): The value to be loaded.
"""
raise NotImplementedError
def __load(self, value: _ValueType) -> _ValueType:
"""
Overview:
Load the value.
Arguments:
- value (:obj:`_ValueType`): The value to be loaded.
"""
return self._load(value)
def __check(self, value: _ValueType) -> bool:
"""
Overview:
Check whether the value is valid.
Arguments:
- value (:obj:`_ValueType`): The value to be checked.
"""
try:
self._load(value)
except CAPTURE_EXCEPTIONS:
return False
else:
return True
def load(self, value: _ValueType) -> _ValueType:
"""
Overview:
Load the value.
Arguments:
- value (:obj:`_ValueType`): The value to be loaded.
"""
return self.__load(value)
def check(self, value: _ValueType) -> bool:
"""
Overview:
Check whether the value is valid.
Arguments:
- value (:obj:`_ValueType`): The value to be checked.
"""
return self.__check(value)
def __call__(self, value: _ValueType) -> _ValueType:
"""
Overview:
Load the value.
Arguments:
- value (:obj:`_ValueType`): The value to be loaded.
"""
return self.__load(value)
def __and__(self, other) -> 'ILoaderClass':
"""
Overview:
Combine two loaders.
Arguments:
- other (:obj:`ILoaderClass`): The other loader.
"""
def _load(value: _ValueType) -> _ValueType:
self.load(value)
return Loader(other).load(value)
return Loader(_load)
def __rand__(self, other) -> 'ILoaderClass':
"""
Overview:
Combine two loaders.
Arguments:
- other (:obj:`ILoaderClass`): The other loader.
"""
return Loader(other) & self
def __or__(self, other) -> 'ILoaderClass':
"""
Overview:
Combine two loaders.
Arguments:
- other (:obj:`ILoaderClass`): The other loader.
"""
def _load(value: _ValueType) -> _ValueType:
try:
return self.load(value)
except CAPTURE_EXCEPTIONS:
return Loader(other).load(value)
return Loader(_load)
def __ror__(self, other) -> 'ILoaderClass':
"""
Overview:
Combine two loaders.
Arguments:
- other (:obj:`ILoaderClass`): The other loader.
"""
return Loader(other) | self
def __rshift__(self, other) -> 'ILoaderClass':
"""
Overview:
Combine two loaders.
Arguments:
- other (:obj:`ILoaderClass`): The other loader.
"""
def _load(value: _ValueType) -> _ValueType:
_return_value = self.load(value)
return _to_loader(other).load(_return_value)
return Loader(_load)
def __rrshift__(self, other) -> 'ILoaderClass':
"""
Overview:
Combine two loaders.
Arguments:
- other (:obj:`ILoaderClass`): The other loader.
"""
return Loader(other) >> self
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