sqlalchemy.types.Boolean

class documentation

class Boolean(Emulated, TypeEngine, SchemaType):

Known subclasses: sqlalchemy.dialects.mssql.BIT, sqlalchemy.sql.sqltypes.MatchType, sqlalchemy.types.BOOLEAN, sqlalchemy.databases.oracle._OracleBoolean, sqlalchemy.dialects.postgresql.asyncpg.AsyncpgBoolean, sqlalchemy.dialects.postgresql.pg8000._PGBoolean

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A bool datatype.

.Boolean typically uses BOOLEAN or SMALLINT on the DDL side, and on the Python side deals in True or False.

The .Boolean datatype currently has two levels of assertion that the values persisted are simple true/false values. For all backends, only the Python values None, True, False, 1 or 0 are accepted as parameter values. For those backends that don't support a "native boolean" datatype, an option exists to also create a CHECK constraint on the target column

Changed in version 1.2: the .Boolean datatype now asserts that incoming Python values are already in pure boolean form.
Method __init__ Construct a Boolean.
Method bind​_processor Return a conversion function for processing bind values.
Method literal​_processor Return a conversion function for processing literal values that are to be rendered directly without using binds.
Method result​_processor Return a conversion function for processing result row values.
Method ​_set​_table Undocumented
Method ​_should​_create​_constraint Undocumented
Method ​_strict​_as​_bool Undocumented
Class Variable __visit​_name__ Undocumented
Class Variable ​_strict​_bools Undocumented
Class Variable native Undocumented
Instance Variable ​_create​_events Undocumented
Instance Variable create​_constraint Undocumented
Instance Variable name Undocumented
Property python​_type Return the Python type object expected to be returned by instances of this type, if known.

Inherited from Emulated:

Method adapt Undocumented
Method adapt​_to​_emulated Given an impl class, adapt this type to the impl assuming "emulated".

Inherited from TypeEngine:

Class ​Comparator Base class for custom comparison operations defined at the type level. See .TypeEngine.comparator_factory.
Method adapt Produce an "adapted" form of this type, given an "impl" class to work with.
Method as​_generic Return an instance of the generic type corresponding to this type using heuristic rule. The method may be overridden if this heuristic rule is not sufficient.
Method bind​_expression Given a bind value (i.e. a .BindParameter instance), return a SQL expression in its place.
Method coerce​_compared​_value Suggest a type for a 'coerced' Python value in an expression.
Method column​_expression Given a SELECT column expression, return a wrapping SQL expression.
Method compare​_against​_backend Compare this type against the given backend type.
Method compare​_values Compare two values for equality.
Method compile Produce a string-compiled form of this .TypeEngine.
Method dialect​_impl Return a dialect-specific implementation for this .TypeEngine.
Method evaluates​_none Return a copy of this type which has the .should_evaluate_none flag set to True.
Method get​_dbapi​_type Return the corresponding type object from the underlying DB-API, if any.
Method with​_variant Produce a new type object that will utilize the given type when applied to the dialect of the given name.
Class Variable hashable Flag, if False, means values from this type aren't hashable.
Class Variable should​_evaluate​_none If True, the Python constant None is considered to be handled explicitly by this type.
Class Variable sort​_key​_function A sorting function that can be passed as the key to sorted.
Static Method ​_to​_instance Undocumented
Method __repr__ Undocumented
Method __str__ Undocumented
Method ​_cached​_bind​_processor Return a dialect-specific bind processor for this type.
Method ​_cached​_custom​_processor Undocumented
Method ​_cached​_literal​_processor Return a dialect-specific literal processor for this type.
Method ​_cached​_result​_processor Return a dialect-specific result processor for this type.
Method ​_compare​_type​_affinity Undocumented
Method ​_default​_dialect Undocumented
Method ​_dialect​_info Return a dialect-specific registry which caches a dialect-specific implementation, bind processing function, and one or more result processing functions.
Method ​_gen​_dialect​_impl Undocumented
Method ​_resolve​_for​_literal adjust this type given a literal Python value that will be stored in a bound parameter.
Method ​_unwrapped​_dialect​_impl Return the 'unwrapped' dialect impl for this type.
Method copy Undocumented
Method copy​_value Undocumented
Class Variable ​_is​_array Undocumented
Class Variable ​_is​_table​_value Undocumented
Class Variable ​_is​_tuple​_type Undocumented
Class Variable ​_is​_type​_decorator Undocumented
Class Variable ​_isnull Undocumented
Class Variable ​_sqla​_type Undocumented
Property ​_generic​_type​_affinity Undocumented
Property ​_has​_bind​_expression memoized boolean, check if bind_expression is implemented.
Property ​_has​_column​_expression memoized boolean, check if column_expression is implemented.
Property ​_static​_cache​_key Undocumented
Property ​_type​_affinity Return a rudimental 'affinity' value expressing the general class of type.

Inherited from Traversible (via TypeEngine):

Method get​_children Return immediate child .visitors.Traversible elements of this .visitors.Traversible.
Method __class​_getitem__ Undocumented

Inherited from SchemaType:

Method ​_is​_impl​_for​_variant Undocumented
Method ​_on​_metadata​_create Undocumented
Method ​_on​_metadata​_drop Undocumented
Method ​_on​_table​_create Undocumented
Method ​_on​_table​_drop Undocumented
Method ​_set​_parent Associate with this SchemaEvent's parent object.
Method ​_variant​_mapping​_for​_set​_table Undocumented
Method adapt Undocumented
Method copy Undocumented
Method create Issue CREATE DDL for this type, if applicable.
Method drop Issue DROP DDL for this type, if applicable.
Class Variable ​_use​_schema​_map Undocumented
Instance Variable inherit​_schema Undocumented
Instance Variable metadata Undocumented
Instance Variable schema Undocumented
Property bind Undocumented

Inherited from SchemaEventTarget (via SchemaType):

Method ​_set​_parent​_with​_dispatch Undocumented
def __init__(self, create_constraint=False, name=None, _create_events=True):
overrides sqlalchemy.sql.sqltypes.SchemaType.__init__
overridden in sqlalchemy.dialects.mysql.types._MatchType
Construct a Boolean.
Parameters
create​_constraint

defaults to False. If the boolean is generated as an int/smallint, also create a CHECK constraint on the table that ensures 1 or 0 as a value.

Note

it is strongly recommended that the CHECK constraint have an explicit name in order to support schema-management concerns. This can be established either by setting the :paramref:`.Boolean.name` parameter or by setting up an appropriate naming convention; see :ref:`constraint_naming_conventions` for background.

Changed in version 1.4: - this flag now defaults to False, meaning no CHECK constraint is generated for a non-native enumerated type.
nameif a CHECK constraint is generated, specify the name of the constraint.
​_create​_eventsUndocumented
def bind_processor(self, dialect):
overrides sqlalchemy.types.TypeEngine.bind_processor

Return a conversion function for processing bind values.

Returns a callable which will receive a bind parameter value as the sole positional argument and will return a value to send to the DB-API.

If processing is not necessary, the method should return None.

Note

This method is only called relative to a dialect specific type object, which is often private to a dialect in use and is not the same type object as the public facing one, which means it's not feasible to subclass a .types.TypeEngine class in order to provide an alternate _types.TypeEngine.bind_processor method, unless subclassing the _types.UserDefinedType class explicitly.

To provide alternate behavior for _types.TypeEngine.bind_processor, implement a _types.TypeDecorator class and provide an implementation of _types.TypeDecorator.process_bind_param.

See Also

:ref:`types_typedecorator`

Parameters
dialectDialect instance in use.
def literal_processor(self, dialect):
overrides sqlalchemy.types.TypeEngine.literal_processor

Return a conversion function for processing literal values that are to be rendered directly without using binds.

This function is used when the compiler makes use of the "literal_binds" flag, typically used in DDL generation as well as in certain scenarios where backends don't accept bound parameters.

Returns a callable which will receive a literal Python value as the sole positional argument and will return a string representation to be rendered in a SQL statement.

Note

This method is only called relative to a dialect specific type object, which is often private to a dialect in use and is not the same type object as the public facing one, which means it's not feasible to subclass a .types.TypeEngine class in order to provide an alternate _types.TypeEngine.literal_processor method, unless subclassing the _types.UserDefinedType class explicitly.

To provide alternate behavior for _types.TypeEngine.literal_processor, implement a _types.TypeDecorator class and provide an implementation of _types.TypeDecorator.process_literal_param.

See Also

:ref:`types_typedecorator`

def result_processor(self, dialect, coltype):
overrides sqlalchemy.types.TypeEngine.result_processor

Return a conversion function for processing result row values.

Returns a callable which will receive a result row column value as the sole positional argument and will return a value to return to the user.

If processing is not necessary, the method should return None.

Note

This method is only called relative to a dialect specific type object, which is often private to a dialect in use and is not the same type object as the public facing one, which means it's not feasible to subclass a .types.TypeEngine class in order to provide an alternate _types.TypeEngine.result_processor method, unless subclassing the _types.UserDefinedType class explicitly.

To provide alternate behavior for _types.TypeEngine.result_processor, implement a _types.TypeDecorator class and provide an implementation of _types.TypeDecorator.process_result_value.

See Also

:ref:`types_typedecorator`

Parameters
dialectDialect instance in use.
coltypeDBAPI coltype argument received in cursor.description.
@util.preload_module('sqlalchemy.sql.schema')
def _set_table(self, column, table):
overrides sqlalchemy.sql.sqltypes.SchemaType._set_table

Undocumented

def _should_create_constraint(self, compiler, **kw):

Undocumented

def _strict_as_bool(self, value):

Undocumented

__visit_name__: str =
overridden in sqlalchemy.dialects.mssql.BIT, sqlalchemy.types.BOOLEAN

Undocumented

_strict_bools =

Undocumented

native: bool =

Undocumented

_create_events =
overrides sqlalchemy.sql.sqltypes.SchemaType._create_events

Undocumented

create_constraint =

Undocumented

name =
overrides sqlalchemy.sql.sqltypes.SchemaType.name

Undocumented

@property
python_type =
overrides sqlalchemy.types.TypeEngine.python_type

Return the Python type object expected to be returned by instances of this type, if known.

Basically, for those types which enforce a return type, or are known across the board to do such for all common DBAPIs (like int for example), will return that type.

If a return type is not defined, raises NotImplementedError.

Note that any type also accommodates NULL in SQL which means you can also get back None from any type in practice.