我们从Python开源项目中，提取了以下50个代码示例，用于说明如何使用sqlalchemy.types.TypeDecorator()。
def coerce_compared_value(self, op, value): """Suggest a type for a 'coerced' Python value in an expression. Given an operator and value, gives the type a chance to return a type which the value should be coerced into. The default behavior here is conservative; if the right-hand side is already coerced into a SQL type based on its Python type, it is usually left alone. End-user functionality extension here should generally be via :class:`.TypeDecorator`, which provides more liberal behavior in that it defaults to coercing the other side of the expression into this type, thus applying special Python conversions above and beyond those needed by the DBAPI to both ides. It also provides the public method :meth:`.TypeDecorator.coerce_compared_value` which is intended for end-user customization of this behavior. """ _coerced_type = _type_map.get(type(value), NULLTYPE) if _coerced_type is NULLTYPE or _coerced_type._type_affinity \ is self._type_affinity: return self else: return _coerced_type
def coerce_compared_value(self, op, value): """Suggest a type for a 'coerced' Python value in an expression. Default behavior for :class:`.UserDefinedType` is the same as that of :class:`.TypeDecorator`; by default it returns ``self``, assuming the compared value should be coerced into the same type as this one. See :meth:`.TypeDecorator.coerce_compared_value` for more detail. .. versionchanged:: 0.8 :meth:`.UserDefinedType.coerce_compared_value` now returns ``self`` by default, rather than falling onto the more fundamental behavior of :meth:`.TypeEngine.coerce_compared_value`. """ return self
def __init__(self, *args, **kwargs): """Construct a :class:`.TypeDecorator`. Arguments sent here are passed to the constructor of the class assigned to the ``impl`` class level attribute, assuming the ``impl`` is a callable, and the resulting object is assigned to the ``self.impl`` instance attribute (thus overriding the class attribute of the same name). If the class level ``impl`` is not a callable (the unusual case), it will be assigned to the same instance attribute 'as-is', ignoring those arguments passed to the constructor. Subclasses can override this to customize the generation of ``self.impl`` entirely. """ if not hasattr(self.__class__, 'impl'): raise AssertionError("TypeDecorator implementations " "require a class-level variable " "'impl' which refers to the class of " "type being decorated") self.impl = to_instance(self.__class__.impl, *args, **kwargs)
def _gen_dialect_impl(self, dialect): """ #todo """ adapted = dialect.type_descriptor(self) if adapted is not self: return adapted # otherwise adapt the impl type, link # to a copy of this TypeDecorator and return # that. typedesc = self.load_dialect_impl(dialect).dialect_impl(dialect) tt = self.copy() if not isinstance(tt, self.__class__): raise AssertionError('Type object %s does not properly ' 'implement the copy() method, it must ' 'return an object of type %s' % (self, self.__class__)) tt.impl = typedesc return tt
def type_engine(self, dialect): """Return a dialect-specific :class:`.TypeEngine` instance for this :class:`.TypeDecorator`. In most cases this returns a dialect-adapted form of the :class:`.TypeEngine` type represented by ``self.impl``. Makes usage of :meth:`dialect_impl` but also traverses into wrapped :class:`.TypeDecorator` instances. Behavior can be customized here by overriding :meth:`load_dialect_impl`. """ adapted = dialect.type_descriptor(self) if not isinstance(adapted, type(self)): return adapted elif isinstance(self.impl, TypeDecorator): return self.impl.type_engine(dialect) else: return self.load_dialect_impl(dialect)
def coerce_compared_value(self, op, value): """Suggest a type for a 'coerced' Python value in an expression. Given an operator and value, gives the type a chance to return a type which the value should be coerced into. The default behavior here is conservative; if the right-hand side is already coerced into a SQL type based on its Python type, it is usually left alone. End-user functionality extension here should generally be via :class:`.TypeDecorator`, which provides more liberal behavior in that it defaults to coercing the other side of the expression into this type, thus applying special Python conversions above and beyond those needed by the DBAPI to both ides. It also provides the public method :meth:`.TypeDecorator.coerce_compared_value` which is intended for end-user customization of this behavior. """ _coerced_type = _resolve_value_to_type(value) if _coerced_type is NULLTYPE or _coerced_type._type_affinity \ is self._type_affinity: return self else: return _coerced_type
def type_engine(self, dialect): """Return a dialect-specific :class:`.TypeEngine` instance for this :class:`.TypeDecorator`. In most cases this returns a dialect-adapted form of the :class:`.TypeEngine` type represented by ``self.impl``. Makes usage of :meth:`dialect_impl` but also traverses into wrapped :class:`.TypeDecorator` instances. Behavior can be customized here by overriding :meth:`load_dialect_impl`. """ adapted = dialect.type_descriptor(self) if type(adapted) is not type(self): return adapted elif isinstance(self.impl, TypeDecorator): return self.impl.type_engine(dialect) else: return self.load_dialect_impl(dialect)
