sqlalchemy.dialects.firebird.VARCHAR

class documentation

class VARCHAR(_StringType, sqltypes.VARCHAR):

View In Hierarchy

Firebird VARCHAR type
Method __init__ Create a string-holding type.
Class Variable __visit​_name__ Undocumented

Inherited from _StringType:

Instance Variable charset Undocumented

Inherited from String (via _StringType):

Method bind​_processor Return a conversion function for processing bind values.
Method get​_dbapi​_type Return the corresponding type object from the underlying DB-API, if any.
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.
Constant RETURNS​_BYTES Undocumented
Constant RETURNS​_CONDITIONAL Undocumented
Constant RETURNS​_UNICODE Undocumented
Constant RETURNS​_UNKNOWN Undocumented
Class Method ​_warn​_deprecated​_unicode Undocumented
Instance Variable ​_expect​_unicode Undocumented
Instance Variable ​_expect​_unicode​_error Undocumented
Instance Variable ​_warn​_on​_bytestring Undocumented
Instance Variable collation Undocumented
Instance Variable length Undocumented
Property python​_type Return the Python type object expected to be returned by instances of this type, if known.

Inherited from Concatenable (via _StringType, String):

Class ​Comparator Undocumented

Inherited from TypeEngine (via _StringType, String):

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 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 _StringType, String, TypeEngine):

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

Inherited from String (via VARCHAR):

Method bind​_processor Return a conversion function for processing bind values.
Method get​_dbapi​_type Return the corresponding type object from the underlying DB-API, if any.
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.
Constant RETURNS​_BYTES Undocumented
Constant RETURNS​_CONDITIONAL Undocumented
Constant RETURNS​_UNICODE Undocumented
Constant RETURNS​_UNKNOWN Undocumented
Class Method ​_warn​_deprecated​_unicode Undocumented
Instance Variable ​_expect​_unicode Undocumented
Instance Variable ​_expect​_unicode​_error Undocumented
Instance Variable ​_warn​_on​_bytestring Undocumented
Instance Variable collation Undocumented
Instance Variable length Undocumented
Property python​_type Return the Python type object expected to be returned by instances of this type, if known.

Inherited from Concatenable (via VARCHAR, String):

Class ​Comparator Undocumented

Inherited from TypeEngine (via VARCHAR, String):

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 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 VARCHAR, String, TypeEngine):

Method get​_children Return immediate child .visitors.Traversible elements of this .visitors.Traversible.
Method __class​_getitem__ Undocumented
def __init__(self, length=None, **kwargs):
overrides sqlalchemy.databases.firebird._StringType.__init__
Create a string-holding type.
Parameters
lengthoptional, a length for the column for use in DDL and CAST expressions. May be safely omitted if no CREATE TABLE will be issued. Certain databases may require a length for use in DDL, and will raise an exception when the CREATE TABLE DDL is issued if a VARCHAR with no length is included. Whether the value is interpreted as bytes or characters is database specific.
**kwargsUndocumented
collation

Optional, a column-level collation for use in DDL and CAST expressions. Renders using the COLLATE keyword supported by SQLite, MySQL, and PostgreSQL. E.g.:

>>> from sqlalchemy import cast, select, String
>>> print(select(cast('some string', String(collation='utf8'))))
SELECT CAST(:param_1 AS VARCHAR COLLATE utf8) AS anon_1
convert​_unicode

When set to True, the .String type will assume that input is to be passed as Python Unicode objects under Python 2, and results returned as Python Unicode objects. In the rare circumstance that the DBAPI does not support Python unicode under Python 2, SQLAlchemy will use its own encoder/decoder functionality on strings, referring to the value of the :paramref:`_sa.create_engine.encoding` parameter parameter passed to _sa.create_engine as the encoding.

For the extremely rare case that Python Unicode is to be encoded/decoded by SQLAlchemy on a backend that does natively support Python Unicode, the string value "force" can be passed here which will cause SQLAlchemy's encode/decode services to be used unconditionally.

Note

SQLAlchemy's unicode-conversion flags and features only apply to Python 2; in Python 3, all string objects are Unicode objects. For this reason, as well as the fact that virtually all modern DBAPIs now support Unicode natively even under Python 2, the :paramref:`.String.convert_unicode` flag is inherently a legacy feature.

Note

In the vast majority of cases, the .Unicode or .UnicodeText datatypes should be used for a _schema.Column that expects to store non-ascii data. These datatypes will ensure that the correct types are used on the database side as well as set up the correct Unicode behaviors under Python 2.

See Also

:paramref:`_sa.create_engine.convert_unicode` - _engine.Engine-wide parameter

unicode​_errorOptional, a method to use to handle Unicode conversion errors. Behaves like the errors keyword argument to the standard library's string.decode() functions, requires that :paramref:`.String.convert_unicode` is set to "force"
__visit_name__: str =
overrides sqlalchemy.types.String.__visit_name__

Undocumented