sqlalchemy.types.Unicode

class documentation

class Unicode(String):

Known subclasses: sqlalchemy.types.NCHAR, sqlalchemy.types.NVARCHAR, sqlalchemy.databases.mssql._MSUnicode, sqlalchemy.dialects.oracle.cx_oracle._OracleUnicodeStringCHAR, sqlalchemy.dialects.sybase.UNICHAR, sqlalchemy.dialects.sybase.UNIVARCHAR

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A variable length Unicode string type.

The .Unicode type is a .String subclass that assumes input and output strings that may contain non-ASCII characters, and for some backends implies an underlying column type that is explicitly supporting of non-ASCII data, such as NVARCHAR on Oracle and SQL Server. This will impact the output of CREATE TABLE statements and CAST functions at the dialect level, and also in some cases will indicate different behavior in the DBAPI itself in how it handles bound parameters.

The character encoding used by the .Unicode type that is used to transmit and receive data to the database is usually determined by the DBAPI itself. All modern DBAPIs accommodate non-ASCII strings but may have different methods of managing database encodings; if necessary, this encoding should be configured as detailed in the notes for the target DBAPI in the :ref:`dialect_toplevel` section.

In modern SQLAlchemy, use of the .Unicode datatype does not typically imply any encoding/decoding behavior within SQLAlchemy itself. Historically, when DBAPIs did not support Python unicode objects under Python 2, SQLAlchemy handled unicode encoding/decoding services itself which would be controlled by the flag :paramref:`.String.convert_unicode`; this flag is deprecated as it is no longer needed for Python 3.

When using Python 2, data that is passed to columns that use the .Unicode datatype must be of type unicode, and not str which in Python 2 is equivalent to bytes. In Python 3, all data passed to columns that use the .Unicode datatype should be of type str. See the flag :paramref:`.String.convert_unicode` for more discussion of unicode encode/decode behavior under Python 2.

Warning

Some database backends, particularly SQL Server with pyodbc, are known to have undesirable behaviors regarding data that is noted as being of NVARCHAR type as opposed to VARCHAR, including datatype mismatch errors and non-use of indexes. See the section on .DialectEvents.do_setinputsizes for background on working around unicode character issues for backends like SQL Server with pyodbc as well as cx_Oracle.

See Also

.UnicodeText - unlengthed textual counterpart to .Unicode.

:paramref:`.String.convert_unicode`

.DialectEvents.do_setinputsizes

Method	`__init__`	Create a `.Unicode` object.
Class Variable	`__visit_name__`	Undocumented

Inherited from String:

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 String):

Class Comparator Undocumented

Inherited from TypeEngine (via 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 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.types.String.__init__

overridden in sqlalchemy.dialects.mysql.types.NCHAR, sqlalchemy.dialects.mysql.types.NVARCHAR

Create a .Unicode object.

Parameters are the same as that of .String, with the exception that convert_unicode defaults to True.

__visit_name__: str =

overrides sqlalchemy.types.String.__visit_name__

overridden in sqlalchemy.types.NCHAR, sqlalchemy.types.NVARCHAR, sqlalchemy.dialects.sybase.UNICHAR, sqlalchemy.dialects.sybase.UNIVARCHAR

Undocumented