SQLAlchemy provides abstractions for most common database data types, and a mechanism for specifying your own custom data types.
The methods and attributes of type objects are rarely used directly.
Type objects are supplied to Table
definitions
and can be supplied as type hints to functions for occasions where
the database driver returns an incorrect type.
>>> users = Table('users', metadata,
... Column('id', Integer, primary_key=True),
... Column('login', String(32))
... )
SQLAlchemy will use the Integer
and String(32)
type
information when issuing a CREATE TABLE
statement and will use it
again when reading back rows SELECTed
from the database.
Functions that accept a type (such as Column()
) will
typically accept a type class or instance; Integer
is equivalent
to Integer()
with no construction arguments in this case.
Generic types specify a column that can read, write and store a
particular type of Python data. SQLAlchemy will choose the best
database column type available on the target database when issuing a
CREATE TABLE
statement. For complete control over which column
type is emitted in CREATE TABLE
, such as VARCHAR
see
SQL Standard and Multiple Vendor Types and the other sections of this chapter.
Object Name | Description |
---|---|
A type for bigger |
|
A bool datatype. |
|
A type for |
|
A type for |
|
Generic Enum Type. |
|
Type representing floating point types, such as |
|
A type for |
|
A type for |
|
A type for large binary byte data. |
|
Refers to the return type of the MATCH operator. |
|
A type for fixed precision numbers, such as |
|
Holds Python objects, which are serialized using pickle. |
|
Mark a type as possibly requiring schema-level DDL for usage. |
|
A type for smaller |
|
The base for all string and character types. |
|
A variably sized string type. |
|
A type for |
|
A variable length Unicode string type. |
|
An unbounded-length Unicode string type. |
sqlalchemy.types.
BigInteger
¶A type for bigger int
integers.
Typically generates a BIGINT
in DDL, and otherwise acts like
a normal Integer
on the Python side.
Class signature
class sqlalchemy.types.BigInteger
(sqlalchemy.types.Integer
)
sqlalchemy.types.
Boolean
(create_constraint=True, name=None, _create_events=True)¶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, a CHECK constraint is also
created on the target column. Production of the CHECK constraint
can be disabled by passing the Boolean.create_constraint
flag set to False
.
Changed in version 1.2: the Boolean
datatype now asserts that
incoming Python values are already in pure boolean form.
Class signature
class sqlalchemy.types.Boolean
(sqlalchemy.types.Emulated
, sqlalchemy.types.TypeEngine
, sqlalchemy.types.SchemaType
)
sqlalchemy.types.Boolean.
__init__
(create_constraint=True, name=None, _create_events=True)¶Construct a Boolean.
sqlalchemy.types.Boolean.
bind_processor
(dialect)¶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
.
dialect¶ – Dialect instance in use.
sqlalchemy.types.Boolean.
literal_processor
(dialect)¶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.
New in version 0.9.0.
sqlalchemy.types.Boolean.
python_type
¶sqlalchemy.types.Boolean.
result_processor
(dialect, coltype)¶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
.
sqlalchemy.types.
Date
¶A type for datetime.date()
objects.
Class signature
class sqlalchemy.types.Date
(sqlalchemy.types._LookupExpressionAdapter
, sqlalchemy.types.TypeEngine
)
sqlalchemy.types.Date.
get_dbapi_type
(dbapi)¶Return the corresponding type object from the underlying DB-API, if any.
This can be useful for calling setinputsizes()
, for example.
sqlalchemy.types.Date.
python_type
¶sqlalchemy.types.
DateTime
(timezone=False)¶A type for datetime.datetime()
objects.
Date and time types return objects from the Python datetime
module. Most DBAPIs have built in support for the datetime
module, with the noted exception of SQLite. In the case of
SQLite, date and time types are stored as strings which are then
converted back to datetime objects when rows are returned.
For the time representation within the datetime type, some
backends include additional options, such as timezone support and
fractional seconds support. For fractional seconds, use the
dialect-specific datatype, such as TIME
. For
timezone support, use at least the TIMESTAMP
datatype,
if not the dialect-specific datatype object.
Class signature
class sqlalchemy.types.DateTime
(sqlalchemy.types._LookupExpressionAdapter
, sqlalchemy.types.TypeEngine
)
sqlalchemy.types.DateTime.
__init__
(timezone=False)¶Construct a new DateTime
.
timezone¶ – boolean. Indicates that the datetime type should
enable timezone support, if available on the
base date/time-holding type only. It is recommended
to make use of the TIMESTAMP
datatype directly when
using this flag, as some databases include separate generic
date/time-holding types distinct from the timezone-capable
TIMESTAMP datatype, such as Oracle.
sqlalchemy.types.DateTime.
get_dbapi_type
(dbapi)¶Return the corresponding type object from the underlying DB-API, if any.
This can be useful for calling setinputsizes()
, for example.
sqlalchemy.types.DateTime.
python_type
¶sqlalchemy.types.
Enum
(*enums, **kw)¶Generic Enum Type.
The Enum
type provides a set of possible string values
which the column is constrained towards.
The Enum
type will make use of the backend’s native “ENUM”
type if one is available; otherwise, it uses a VARCHAR datatype and
produces a CHECK constraint. Use of the backend-native enum type
can be disabled using the Enum.native_enum
flag, and
the production of the CHECK constraint is configurable using the
Enum.create_constraint
flag.
The Enum
type also provides in-Python validation of string
values during both read and write operations. When reading a value
from the database in a result set, the string value is always checked
against the list of possible values and a LookupError
is raised
if no match is found. When passing a value to the database as a
plain string within a SQL statement, if the
Enum.validate_strings
parameter is
set to True, a LookupError
is raised for any string value that’s
not located in the given list of possible values; note that this
impacts usage of LIKE expressions with enumerated values (an unusual
use case).
Changed in version 1.1: the Enum
type now provides in-Python
validation of input values as well as on data being returned by
the database.
The source of enumerated values may be a list of string values, or
alternatively a PEP-435-compliant enumerated class. For the purposes
of the Enum
datatype, this class need only provide a
__members__
method.
When using an enumerated class, the enumerated objects are used both for input and output, rather than strings as is the case with a plain-string enumerated type:
import enum
class MyEnum(enum.Enum):
one = 1
two = 2
three = 3
t = Table(
'data', MetaData(),
Column('value', Enum(MyEnum))
)
connection.execute(t.insert(), {"value": MyEnum.two})
assert connection.scalar(t.select()) is MyEnum.two
Above, the string names of each element, e.g. “one”, “two”, “three”, are persisted to the database; the values of the Python Enum, here indicated as integers, are not used; the value of each enum can therefore be any kind of Python object whether or not it is persistable.
In order to persist the values and not the names, the
Enum.values_callable
parameter may be used. The value of
this parameter is a user-supplied callable, which is intended to be used
with a PEP-435-compliant enumerated class and returns a list of string
values to be persisted. For a simple enumeration that uses string values,
a callable such as lambda x: [e.value for e in x]
is sufficient.
New in version 1.1: - support for PEP-435-style enumerated classes.
See also
ENUM
- PostgreSQL-specific type,
which has additional functionality.
ENUM
- MySQL-specific type
Class signature
class sqlalchemy.types.Enum
(sqlalchemy.types.Emulated
, sqlalchemy.types.String
, sqlalchemy.types.SchemaType
)
sqlalchemy.types.Enum.
__init__
(*enums, **kw)¶Construct an enum.
Keyword arguments which don’t apply to a specific backend are ignored by that backend.
*enums¶ –
either exactly one PEP-435 compliant enumerated type or one or more string or unicode enumeration labels. If unicode labels are present, the convert_unicode flag is auto-enabled.
New in version 1.1: a PEP-435 style enumerated class may be passed.
convert_unicode¶ –
Enable unicode-aware bind parameter and result-set processing for this Enum’s data. This is set automatically based on the presence of unicode label strings.
Deprecated since version 1.3: The Enum.convert_unicode
parameter is deprecated and will be removed in a future release. All modern DBAPIs now support Python Unicode directly and this parameter is unnecessary.
create_constraint¶ –
defaults to True. When creating a non-native enumerated type, also build a CHECK constraint on the database against the valid values.
New in version 1.1: - added Enum.create_constraint
which provides the option to disable the production of the
CHECK constraint for a non-native enumerated type.
metadata¶ – Associate this type directly with a MetaData
object. For types that exist on the target database as an
independent schema construct (PostgreSQL), this type will be
created and dropped within create_all()
and drop_all()
operations. If the type is not associated with any MetaData
object, it will associate itself with each Table
in which it is
used, and will be created when any of those individual tables are
created, after a check is performed for its existence. The type is
only dropped when drop_all()
is called for that Table
object’s metadata, however.
name¶ – The name of this type. This is required for PostgreSQL and any future supported database which requires an explicitly named type, or an explicitly named constraint in order to generate the type and/or a table that uses it. If a PEP-435 enumerated class was used, its name (converted to lower case) is used by default.
native_enum¶ – Use the database’s native ENUM type when
available. Defaults to True. When False, uses VARCHAR + check
constraint for all backends. The VARCHAR length can be controlled
with Enum.length
length¶ –
Allows specifying a custom length for the VARCHAR
when Enum.native_enum
is False. By default it uses the
length of the longest value.
New in version 1.3.16.
schema¶ –
Schema name of this type. For types that exist on the target database as an independent schema construct (PostgreSQL), this parameter specifies the named schema in which the type is present.
quote¶ – Set explicit quoting preferences for the type’s name.
inherit_schema¶ – When True
, the “schema” from the owning
Table
will be copied to the “schema” attribute of this
Enum
, replacing whatever value was passed for the
schema
attribute. This also takes effect when using the
Table.tometadata()
operation.
validate_strings¶ –
when True, string values that are being
passed to the database in a SQL statement will be checked
for validity against the list of enumerated values. Unrecognized
values will result in a LookupError
being raised.
New in version 1.1.0b2.
values_callable¶ –
A callable which will be passed the PEP-435 compliant enumerated type, which should then return a list of string values to be persisted. This allows for alternate usages such as using the string value of an enum to be persisted to the database instead of its name.
New in version 1.2.3.
sort_key_function¶ –
a Python callable which may be used as the
“key” argument in the Python sorted()
built-in. The SQLAlchemy
ORM requires that primary key columns which are mapped must
be sortable in some way. When using an unsortable enumeration
object such as a Python 3 Enum
object, this parameter may be
used to set a default sort key function for the objects. By
default, the database value of the enumeration is used as the
sorting function.
New in version 1.3.8.
sqlalchemy.types.Enum.
create
(bind=None, checkfirst=False)¶inherited from the SchemaType.create()
method of SchemaType
Issue CREATE DDL for this type, if applicable.
sqlalchemy.types.Enum.
drop
(bind=None, checkfirst=False)¶inherited from the SchemaType.drop()
method of SchemaType
Issue DROP DDL for this type, if applicable.
sqlalchemy.types.
Float
(precision=None, asdecimal=False, decimal_return_scale=None)¶Type representing floating point types, such as FLOAT
or REAL
.
This type returns Python float
objects by default, unless the
Float.asdecimal
flag is set to True, in which case they
are coerced to decimal.Decimal
objects.
Note
The Float
type is designed to receive data from a database
type that is explicitly known to be a floating point type
(e.g. FLOAT
, REAL
, others)
and not a decimal type (e.g. DECIMAL
, NUMERIC
, others).
If the database column on the server is in fact a Numeric
type, such as DECIMAL
or NUMERIC
, use the Numeric
type or a subclass, otherwise numeric coercion between
float
/Decimal
may or may not function as expected.
Class signature
sqlalchemy.types.Float.
__init__
(precision=None, asdecimal=False, decimal_return_scale=None)¶Construct a Float.
precision¶ – the numeric precision for use in DDL CREATE
TABLE
.
asdecimal¶ – the same flag as that of Numeric
, but
defaults to False
. Note that setting this flag to True
results in floating point conversion.
decimal_return_scale¶ –
Default scale to use when converting from floats to Python decimals. Floating point values will typically be much longer due to decimal inaccuracy, and most floating point database types don’t have a notion of “scale”, so by default the float type looks for the first ten decimal places when converting. Specifying this value will override that length. Note that the MySQL float types, which do include “scale”, will use “scale” as the default for decimal_return_scale, if not otherwise specified.
New in version 0.9.0.
sqlalchemy.types.Float.
result_processor
(dialect, coltype)¶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
.
sqlalchemy.types.
Integer
¶A type for int
integers.
Class signature
class sqlalchemy.types.Integer
(sqlalchemy.types._LookupExpressionAdapter
, sqlalchemy.types.TypeEngine
)
sqlalchemy.types.Integer.
get_dbapi_type
(dbapi)¶Return the corresponding type object from the underlying DB-API, if any.
This can be useful for calling setinputsizes()
, for example.
sqlalchemy.types.Integer.
literal_processor
(dialect)¶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.
New in version 0.9.0.
sqlalchemy.types.Integer.
python_type
¶sqlalchemy.types.
Interval
(native=True, second_precision=None, day_precision=None)¶A type for datetime.timedelta()
objects.
The Interval type deals with datetime.timedelta
objects. In
PostgreSQL, the native INTERVAL
type is used; for others, the
value is stored as a date which is relative to the “epoch”
(Jan. 1, 1970).
Note that the Interval
type does not currently provide date arithmetic
operations on platforms which do not support interval types natively. Such
operations usually require transformation of both sides of the expression
(such as, conversion of both sides into integer epoch values first) which
currently is a manual procedure (such as via
expression.func
).
Class signature
class sqlalchemy.types.Interval
(sqlalchemy.types.Emulated
, sqlalchemy.types._AbstractInterval
, sqlalchemy.types.TypeDecorator
)
sqlalchemy.types.Interval.
__init__
(native=True, second_precision=None, day_precision=None)¶Construct an Interval object.
native¶ – when True, use the actual INTERVAL type provided by the database, if supported (currently PostgreSQL, Oracle). Otherwise, represent the interval data as an epoch value regardless.
second_precision¶ – For native interval types which support a “fractional seconds precision” parameter, i.e. Oracle and PostgreSQL
day_precision¶ – for native interval types which support a “day precision” parameter, i.e. Oracle.
sqlalchemy.types.Interval.
adapt_to_emulated
(impltype, **kw)¶Given an impl class, adapt this type to the impl assuming “emulated”.
The impl should also be an “emulated” version of this type, most likely the same class as this type itself.
e.g.: sqltypes.Enum adapts to the Enum class.
sqlalchemy.types.Interval.
bind_processor
(dialect)¶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
.
dialect¶ – Dialect instance in use.
sqlalchemy.types.Interval.
impl
¶alias of sqlalchemy.sql.sqltypes.DateTime
sqlalchemy.types.Interval.
python_type
¶sqlalchemy.types.Interval.
result_processor
(dialect, coltype)¶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
.
sqlalchemy.types.
LargeBinary
(length=None)¶A type for large binary byte data.
The LargeBinary
type corresponds to a large and/or unlengthed
binary type for the target platform, such as BLOB on MySQL and BYTEA for
PostgreSQL. It also handles the necessary conversions for the DBAPI.
Class signature
class sqlalchemy.types.LargeBinary
(sqlalchemy.types._Binary
)
sqlalchemy.types.LargeBinary.
__init__
(length=None)¶Construct a LargeBinary type.
length¶ – optional, a length for the column for use in DDL statements, for those binary types that accept a length, such as the MySQL BLOB type.
sqlalchemy.types.
MatchType
(create_constraint=True, name=None, _create_events=True)¶Refers to the return type of the MATCH operator.
As the ColumnOperators.match()
is probably the most open-ended
operator in generic SQLAlchemy Core, we can’t assume the return type
at SQL evaluation time, as MySQL returns a floating point, not a boolean,
and other backends might do something different. So this type
acts as a placeholder, currently subclassing Boolean
.
The type allows dialects to inject result-processing functionality
if needed, and on MySQL will return floating-point values.
New in version 1.0.0.
Class signature
sqlalchemy.types.
Numeric
(precision=None, scale=None, decimal_return_scale=None, asdecimal=True)¶A type for fixed precision numbers, such as NUMERIC
or DECIMAL
.
This type returns Python decimal.Decimal
objects by default, unless
the Numeric.asdecimal
flag is set to False, in which case
they are coerced to Python float
objects.
Note
The Numeric
type is designed to receive data from a database
type that is explicitly known to be a decimal type
(e.g. DECIMAL
, NUMERIC
, others) and not a floating point
type (e.g. FLOAT
, REAL
, others).
If the database column on the server is in fact a floating-point
type, such as FLOAT
or REAL
, use the Float
type or a subclass, otherwise numeric coercion between
float
/Decimal
may or may not function as expected.
Note
The Python decimal.Decimal
class is generally slow
performing; cPython 3.3 has now switched to use the cdecimal library natively. For
older Python versions, the cdecimal
library can be patched
into any application where it will replace the decimal
library fully, however this needs to be applied globally and
before any other modules have been imported, as follows:
import sys
import cdecimal
sys.modules["decimal"] = cdecimal
Note that the cdecimal
and decimal
libraries are not
compatible with each other, so patching cdecimal
at the
global level is the only way it can be used effectively with
various DBAPIs that hardcode to import the decimal
library.
Class signature
class sqlalchemy.types.Numeric
(sqlalchemy.types._LookupExpressionAdapter
, sqlalchemy.types.TypeEngine
)
sqlalchemy.types.Numeric.
__init__
(precision=None, scale=None, decimal_return_scale=None, asdecimal=True)¶Construct a Numeric.
precision¶ – the numeric precision for use in DDL CREATE
TABLE
.
scale¶ – the numeric scale for use in DDL CREATE TABLE
.
asdecimal¶ – default True. Return whether or not values should be sent as Python Decimal objects, or as floats. Different DBAPIs send one or the other based on datatypes - the Numeric type will ensure that return values are one or the other across DBAPIs consistently.
decimal_return_scale¶ –
Default scale to use when converting
from floats to Python decimals. Floating point values will typically
be much longer due to decimal inaccuracy, and most floating point
database types don’t have a notion of “scale”, so by default the
float type looks for the first ten decimal places when converting.
Specifying this value will override that length. Types which
do include an explicit “.scale” value, such as the base
Numeric
as well as the MySQL float types, will use the
value of “.scale” as the default for decimal_return_scale, if not
otherwise specified.
New in version 0.9.0.
When using the Numeric
type, care should be taken to ensure
that the asdecimal setting is appropriate for the DBAPI in use -
when Numeric applies a conversion from Decimal->float or float->
Decimal, this conversion incurs an additional performance overhead
for all result columns received.
DBAPIs that return Decimal natively (e.g. psycopg2) will have
better accuracy and higher performance with a setting of True
,
as the native translation to Decimal reduces the amount of floating-
point issues at play, and the Numeric type itself doesn’t need
to apply any further conversions. However, another DBAPI which
returns floats natively will incur an additional conversion
overhead, and is still subject to floating point data loss - in
which case asdecimal=False
will at least remove the extra
conversion overhead.
sqlalchemy.types.Numeric.
bind_processor
(dialect)¶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
.
dialect¶ – Dialect instance in use.
sqlalchemy.types.Numeric.
get_dbapi_type
(dbapi)¶Return the corresponding type object from the underlying DB-API, if any.
This can be useful for calling setinputsizes()
, for example.
sqlalchemy.types.Numeric.
literal_processor
(dialect)¶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.
New in version 0.9.0.
sqlalchemy.types.Numeric.
python_type
¶sqlalchemy.types.Numeric.
result_processor
(dialect, coltype)¶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
.
sqlalchemy.types.
PickleType
(protocol=5, pickler=None, comparator=None)¶Holds Python objects, which are serialized using pickle.
PickleType builds upon the Binary type to apply Python’s
pickle.dumps()
to incoming objects, and pickle.loads()
on
the way out, allowing any pickleable Python object to be stored as
a serialized binary field.
To allow ORM change events to propagate for elements associated
with PickleType
, see Mutation Tracking.
Class signature
class sqlalchemy.types.PickleType
(sqlalchemy.types.TypeDecorator
)
sqlalchemy.types.PickleType.
__init__
(protocol=5, pickler=None, comparator=None)¶Construct a PickleType.
protocol¶ – defaults to pickle.HIGHEST_PROTOCOL
.
pickler¶ – defaults to cPickle.pickle or pickle.pickle if
cPickle is not available. May be any object with
pickle-compatible dumps
and loads
methods.
comparator¶ – a 2-arg callable predicate used
to compare values of this type. If left as None
,
the Python “equals” operator is used to compare values.
sqlalchemy.types.PickleType.
bind_processor
(dialect)¶Provide a bound value processing function for the
given Dialect
.
This is the method that fulfills the TypeEngine
contract for bound value conversion. TypeDecorator
will wrap a user-defined implementation of
process_bind_param()
here.
User-defined code can override this method directly,
though its likely best to use process_bind_param()
so that
the processing provided by self.impl
is maintained.
dialect¶ – Dialect instance in use.
This method is the reverse counterpart to the
result_processor()
method of this class.
sqlalchemy.types.PickleType.
compare_values
(x, y)¶Given two values, compare them for equality.
By default this calls upon TypeEngine.compare_values()
of the underlying “impl”, which in turn usually
uses the Python equals operator ==
.
This function is used by the ORM to compare an original-loaded value with an intercepted “changed” value, to determine if a net change has occurred.
sqlalchemy.types.PickleType.
impl
¶alias of sqlalchemy.sql.sqltypes.LargeBinary
sqlalchemy.types.PickleType.
result_processor
(dialect, coltype)¶Provide a result value processing function for the given
Dialect
.
This is the method that fulfills the TypeEngine
contract for result value conversion. TypeDecorator
will wrap a user-defined implementation of
process_result_value()
here.
User-defined code can override this method directly,
though its likely best to use process_result_value()
so that
the processing provided by self.impl
is maintained.
This method is the reverse counterpart to the
bind_processor()
method of this class.
sqlalchemy.types.
SchemaType
(name=None, schema=None, metadata=None, inherit_schema=False, quote=None, _create_events=True)¶Mark a type as possibly requiring schema-level DDL for usage.
Supports types that must be explicitly created/dropped (i.e. PG ENUM type) as well as types that are complimented by table or schema level constraints, triggers, and other rules.
SchemaType
classes can also be targets for the
DDLEvents.before_parent_attach()
and
DDLEvents.after_parent_attach()
events, where the events fire off
surrounding the association of the type object with a parent
Column
.
Class signature
class sqlalchemy.types.SchemaType
(sqlalchemy.sql.expression.SchemaEventTarget
)
sqlalchemy.types.SchemaType.
adapt
(impltype, **kw)¶sqlalchemy.types.SchemaType.
bind
¶sqlalchemy.types.SchemaType.
copy
(**kw)¶sqlalchemy.types.SchemaType.
create
(bind=None, checkfirst=False)¶Issue CREATE DDL for this type, if applicable.
sqlalchemy.types.SchemaType.
drop
(bind=None, checkfirst=False)¶Issue DROP DDL for this type, if applicable.
sqlalchemy.types.
SmallInteger
¶A type for smaller int
integers.
Typically generates a SMALLINT
in DDL, and otherwise acts like
a normal Integer
on the Python side.
Class signature
class sqlalchemy.types.SmallInteger
(sqlalchemy.types.Integer
)
sqlalchemy.types.
String
(length=None, collation=None, convert_unicode=False, unicode_error=None, _warn_on_bytestring=False, _expect_unicode=False)¶The base for all string and character types.
In SQL, corresponds to VARCHAR. Can also take Python unicode objects and encode to the database’s encoding in bind params (and the reverse for result sets.)
The length field is usually required when the String type is used within a CREATE TABLE statement, as VARCHAR requires a length on most databases.
Class signature
class sqlalchemy.types.String
(sqlalchemy.types.Concatenable
, sqlalchemy.types.TypeEngine
)
sqlalchemy.types.String.
__init__
(length=None, collation=None, convert_unicode=False, unicode_error=None, _warn_on_bytestring=False, _expect_unicode=False)¶Create a string-holding type.
length¶ – optional, 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.
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 create_engine.encoding
parameter
parameter passed to create_engine()
as the encoding.
Deprecated since version 1.3: The String.convert_unicode
parameter is deprecated and will be removed in a future release. All modern DBAPIs now support Python Unicode directly and this parameter is unnecessary.
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 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
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
create_engine.convert_unicode
-
Engine
-wide parameter
unicode_error¶ –
Optional, 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 String.convert_unicode
is set to
"force"
Deprecated since version 1.3: The String.unicode_errors
parameter is deprecated and will be removed in a future release. This parameter is unnecessary for modern Python DBAPIs and degrades performance significantly.
sqlalchemy.types.String.
bind_processor
(dialect)¶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
.
dialect¶ – Dialect instance in use.
sqlalchemy.types.String.
get_dbapi_type
(dbapi)¶Return the corresponding type object from the underlying DB-API, if any.
This can be useful for calling setinputsizes()
, for example.
sqlalchemy.types.String.
literal_processor
(dialect)¶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.
New in version 0.9.0.
sqlalchemy.types.String.
python_type
¶sqlalchemy.types.String.
result_processor
(dialect, coltype)¶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
.
sqlalchemy.types.
Text
(length=None, collation=None, convert_unicode=False, unicode_error=None, _warn_on_bytestring=False, _expect_unicode=False)¶A variably sized string type.
In SQL, usually corresponds to CLOB or TEXT. Can also take Python unicode objects and encode to the database’s encoding in bind params (and the reverse for result sets.) In general, TEXT objects do not have a length; while some databases will accept a length argument here, it will be rejected by others.
Class signature
sqlalchemy.types.
Time
(timezone=False)¶A type for datetime.time()
objects.
Class signature
class sqlalchemy.types.Time
(sqlalchemy.types._LookupExpressionAdapter
, sqlalchemy.types.TypeEngine
)
sqlalchemy.types.Time.
get_dbapi_type
(dbapi)¶Return the corresponding type object from the underlying DB-API, if any.
This can be useful for calling setinputsizes()
, for example.
sqlalchemy.types.Time.
python_type
¶sqlalchemy.types.
Unicode
(length=None, **kwargs)¶A variable length Unicode string type.
The Unicode
type is a String
subclass
that assumes input and output as Python unicode
data,
and in that regard is equivalent to the usage of the
convert_unicode
flag with the String
type.
However, unlike plain String
, it also implies an
underlying column type that is explicitly supporting of non-ASCII
data, such as NVARCHAR
on Oracle and SQL Server.
This can impact the output of CREATE TABLE
statements
and CAST
functions at the dialect level, and can
also affect the handling of bound parameters in some
specific DBAPI scenarios.
The encoding used by the Unicode
type is usually
determined by the DBAPI itself; most modern DBAPIs
feature support for Python unicode
objects as bound
values and result set values, and the encoding should
be configured as detailed in the notes for the target
DBAPI in the Dialects section.
For those DBAPIs which do not support, or are not configured
to accommodate Python unicode
objects
directly, SQLAlchemy does the encoding and decoding
outside of the DBAPI. The encoding in this scenario
is determined by the encoding
flag passed to
create_engine()
.
When using the Unicode
type, it is only appropriate
to pass Python unicode
objects, and not plain str
.
If a plain str
is passed under Python 2, a warning
is emitted. If you notice your application emitting these warnings but
you’re not sure of the source of them, the Python
warnings
filter, documented at
http://docs.python.org/library/warnings.html,
can be used to turn these warnings into exceptions
which will illustrate a stack trace:
import warnings
warnings.simplefilter('error')
For an application that wishes to pass plain bytestrings
and Python unicode
objects to the Unicode
type
equally, the bytestrings must first be decoded into
unicode. The recipe at Coercing Encoded Strings to Unicode illustrates
how this is done.
See also
UnicodeText
- unlengthed textual counterpart
to Unicode
.
Class signature
sqlalchemy.types.Unicode.
__init__
(length=None, **kwargs)¶Create a Unicode
object.
Parameters are the same as that of String
,
with the exception that convert_unicode
defaults to True
.
sqlalchemy.types.
UnicodeText
(length=None, **kwargs)¶An unbounded-length Unicode string type.
See Unicode
for details on the unicode
behavior of this object.
Like Unicode
, usage the UnicodeText
type implies a
unicode-capable type being used on the backend, such as
NCLOB
, NTEXT
.
Class signature
sqlalchemy.types.UnicodeText.
__init__
(length=None, **kwargs)¶Create a Unicode-converting Text type.
Parameters are the same as that of TextClause
,
with the exception that convert_unicode
defaults to True
.
This category of types refers to types that are either part of the
SQL standard, or are potentially found within a subset of database backends.
Unlike the “generic” types, the SQL standard/multi-vendor types have no
guarantee of working on all backends, and will only work on those backends
that explicitly support them by name. That is, the type will always emit
its exact name in DDL with CREATE TABLE
is issued.
Object Name | Description |
---|---|
Represent a SQL Array type. |
|
The SQL BIGINT type. |
|
The SQL BINARY type. |
|
The SQL BLOB type. |
|
The SQL BOOLEAN type. |
|
The SQL CHAR type. |
|
The CLOB type. |
|
The SQL DATE type. |
|
The SQL DATETIME type. |
|
The SQL DECIMAL type. |
|
The SQL FLOAT type. |
|
alias of |
|
The SQL INT or INTEGER type. |
|
Represent a SQL JSON type. |
|
The SQL NCHAR type. |
|
The SQL NUMERIC type. |
|
The SQL NVARCHAR type. |
|
The SQL REAL type. |
|
The SQL SMALLINT type. |
|
The SQL TEXT type. |
|
The SQL TIME type. |
|
The SQL TIMESTAMP type. |
|
The SQL VARBINARY type. |
|
The SQL VARCHAR type. |
sqlalchemy.types.
ARRAY
(item_type, as_tuple=False, dimensions=None, zero_indexes=False)¶Represent a SQL Array type.
Note
This type serves as the basis for all ARRAY operations.
However, currently only the PostgreSQL backend has support
for SQL arrays in SQLAlchemy. It is recommended to use the
ARRAY
type directly when using ARRAY types
with PostgreSQL, as it provides additional operators specific
to that backend.
ARRAY
is part of the Core in support of various SQL
standard functions such as array_agg
which explicitly involve
arrays; however, with the exception of the PostgreSQL backend and possibly
some third-party dialects, no other SQLAlchemy built-in dialect has support
for this type.
An ARRAY
type is constructed given the “type”
of element:
mytable = Table("mytable", metadata,
Column("data", ARRAY(Integer))
)
The above type represents an N-dimensional array, meaning a supporting backend such as PostgreSQL will interpret values with any number of dimensions automatically. To produce an INSERT construct that passes in a 1-dimensional array of integers:
connection.execute(
mytable.insert(),
data=[1,2,3]
)
The ARRAY
type can be constructed given a fixed number
of dimensions:
mytable = Table("mytable", metadata,
Column("data", ARRAY(Integer, dimensions=2))
)
Sending a number of dimensions is optional, but recommended if the datatype is to represent arrays of more than one dimension. This number is used:
When emitting the type declaration itself to the database, e.g.
INTEGER[][]
When translating Python values to database values, and vice versa, e.g.
an ARRAY of Unicode
objects uses this number to efficiently
access the string values inside of array structures without resorting
to per-row type inspection
When used with the Python getitem
accessor, the number of dimensions
serves to define the kind of type that the []
operator should
return, e.g. for an ARRAY of INTEGER with two dimensions:
>>> expr = table.c.column[5] # returns ARRAY(Integer, dimensions=1)
>>> expr = expr[6] # returns Integer
For 1-dimensional arrays, an ARRAY
instance with no
dimension parameter will generally assume single-dimensional behaviors.
SQL expressions of type ARRAY
have support for “index” and
“slice” behavior. The Python []
operator works normally here, given
integer indexes or slices. Arrays default to 1-based indexing.
The operator produces binary expression
constructs which will produce the appropriate SQL, both for
SELECT statements:
select([mytable.c.data[5], mytable.c.data[2:7]])
as well as UPDATE statements when the Update.values()
method
is used:
mytable.update().values({
mytable.c.data[5]: 7,
mytable.c.data[2:7]: [1, 2, 3]
})
The ARRAY
type also provides for the operators
Comparator.any()
and
Comparator.all()
. The PostgreSQL-specific version of
ARRAY
also provides additional operators.
New in version 1.1.0.
See also
Class signature
class sqlalchemy.types.ARRAY
(sqlalchemy.sql.expression.SchemaEventTarget
, sqlalchemy.types.Indexable
, sqlalchemy.types.Concatenable
, sqlalchemy.types.TypeEngine
)
Comparator
(expr)¶Define comparison operations for ARRAY
.
More operators are available on the dialect-specific form
of this type. See Comparator
.
Class signature
class sqlalchemy.types.ARRAY.Comparator
(sqlalchemy.types.Comparator
, sqlalchemy.types.Comparator
)
sqlalchemy.types.ARRAY.Comparator.
all
(elements, other, operator=None)¶Return other operator ALL (array)
clause.
Argument places are switched, because ALL requires array expression to be on the right hand-side.
E.g.:
from sqlalchemy.sql import operators
conn.execute(
select([table.c.data]).where(
table.c.data.all(7, operator=operators.lt)
)
)
sqlalchemy.types.ARRAY.Comparator.
any
(elements, other, operator=None)¶Return other operator ANY (array)
clause.
Argument places are switched, because ANY requires array expression to be on the right hand-side.
E.g.:
from sqlalchemy.sql import operators
conn.execute(
select([table.c.data]).where(
table.c.data.any(7, operator=operators.lt)
)
)
sqlalchemy.types.ARRAY.Comparator.
contains
(*arg, **kw)¶Implement the ‘contains’ operator.
Produces a LIKE expression that tests against a match for the middle of a string value:
column LIKE '%' || <other> || '%'
E.g.:
stmt = select([sometable]).\
where(sometable.c.column.contains("foobar"))
Since the operator uses LIKE
, wildcard characters
"%"
and "_"
that are present inside the <other> expression
will behave like wildcards as well. For literal string
values, the ColumnOperators.contains.autoescape
flag
may be set to True
to apply escaping to occurrences of these
characters within the string value so that they match as themselves
and not as wildcard characters. Alternatively, the
ColumnOperators.contains.escape
parameter will establish
a given character as an escape character which can be of use when
the target expression is not a literal string.
other¶ – expression to be compared. This is usually a plain
string value, but can also be an arbitrary SQL expression. LIKE
wildcard characters %
and _
are not escaped by default unless
the ColumnOperators.contains.autoescape
flag is
set to True.
autoescape¶ –
boolean; when True, establishes an escape character
within the LIKE expression, then applies it to all occurrences of
"%"
, "_"
and the escape character itself within the
comparison value, which is assumed to be a literal string and not a
SQL expression.
An expression such as:
somecolumn.contains("foo%bar", autoescape=True)
Will render as:
somecolumn LIKE '%' || :param || '%' ESCAPE '/'
With the value of :param
as "foo/%bar"
.
New in version 1.2.
Changed in version 1.2.0: The
ColumnOperators.contains.autoescape
parameter is
now a simple boolean rather than a character; the escape
character itself is also escaped, and defaults to a forwards
slash, which itself can be customized using the
ColumnOperators.contains.escape
parameter.
escape¶ –
a character which when given will render with the
ESCAPE
keyword to establish that character as the escape
character. This character can then be placed preceding occurrences
of %
and _
to allow them to act as themselves and not
wildcard characters.
An expression such as:
somecolumn.contains("foo/%bar", escape="^")
Will render as:
somecolumn LIKE '%' || :param || '%' ESCAPE '^'
The parameter may also be combined with
ColumnOperators.contains.autoescape
:
somecolumn.contains("foo%bar^bat", escape="^", autoescape=True)
Where above, the given literal parameter will be converted to
"foo^%bar^^bat"
before being passed to the database.
sqlalchemy.types.ARRAY.
__init__
(item_type, as_tuple=False, dimensions=None, zero_indexes=False)¶Construct an ARRAY
.
E.g.:
Column('myarray', ARRAY(Integer))
Arguments are:
item_type¶ – The data type of items of this array. Note that
dimensionality is irrelevant here, so multi-dimensional arrays like
INTEGER[][]
, are constructed as ARRAY(Integer)
, not as
ARRAY(ARRAY(Integer))
or such.
as_tuple=False¶ – Specify whether return results should be converted to tuples from lists. This parameter is not generally needed as a Python list corresponds well to a SQL array.
dimensions¶ – if non-None, the ARRAY will assume a fixed
number of dimensions. This impacts how the array is declared
on the database, how it goes about interpreting Python and
result values, as well as how expression behavior in conjunction
with the “getitem” operator works. See the description at
ARRAY
for additional detail.
zero_indexes=False¶ – when True, index values will be converted between Python zero-based and SQL one-based indexes, e.g. a value of one will be added to all index values before passing to the database.
sqlalchemy.types.ARRAY.
comparator_factory
¶alias of sqlalchemy.sql.sqltypes.ARRAY.Comparator
sqlalchemy.types.ARRAY.
compare_values
(x, y)¶Compare two values for equality.
sqlalchemy.types.ARRAY.
hashable
¶Flag, if False, means values from this type aren’t hashable.
Used by the ORM when uniquing result lists.
sqlalchemy.types.ARRAY.
python_type
¶sqlalchemy.types.ARRAY.
zero_indexes
= False¶If True, Python zero-based indexes should be interpreted as one-based on the SQL expression side.
sqlalchemy.types.
BIGINT
¶The SQL BIGINT type.
Class signature
sqlalchemy.types.
BINARY
(length=None)¶The SQL BINARY type.
Class signature
class sqlalchemy.types.BINARY
(sqlalchemy.types._Binary
)
sqlalchemy.types.
BLOB
(length=None)¶The SQL BLOB type.
Class signature
sqlalchemy.types.
BOOLEAN
(create_constraint=True, name=None, _create_events=True)¶The SQL BOOLEAN type.
Class signature
sqlalchemy.types.
CHAR
(length=None, collation=None, convert_unicode=False, unicode_error=None, _warn_on_bytestring=False, _expect_unicode=False)¶The SQL CHAR type.
Class signature
sqlalchemy.types.
CLOB
(length=None, collation=None, convert_unicode=False, unicode_error=None, _warn_on_bytestring=False, _expect_unicode=False)¶The CLOB type.
This type is found in Oracle and Informix.
Class signature
sqlalchemy.types.
DATE
¶The SQL DATE type.
Class signature
sqlalchemy.types.
DATETIME
(timezone=False)¶The SQL DATETIME type.
Class signature
sqlalchemy.types.
DECIMAL
(precision=None, scale=None, decimal_return_scale=None, asdecimal=True)¶The SQL DECIMAL type.
Class signature
sqlalchemy.types.
FLOAT
(precision=None, asdecimal=False, decimal_return_scale=None)¶The SQL FLOAT type.
Class signature
sqlalchemy.types..
sqlalchemy.types.
INT
¶alias of sqlalchemy.sql.sqltypes.INTEGER
sqlalchemy.types.
JSON
(none_as_null=False)¶Represent a SQL JSON type.
Note
JSON
is provided as a facade for vendor-specific
JSON types. Since it supports JSON SQL operations, it only
works on backends that have an actual JSON type, currently:
PostgreSQL
MySQL as of version 5.7 (MariaDB as of the 10.2 series does not)
SQLite as of version 3.9
JSON
is part of the Core in support of the growing
popularity of native JSON datatypes.
The JSON
type stores arbitrary JSON format data, e.g.:
data_table = Table('data_table', metadata,
Column('id', Integer, primary_key=True),
Column('data', JSON)
)
with engine.connect() as conn:
conn.execute(
data_table.insert(),
data = {"key1": "value1", "key2": "value2"}
)
JSON-Specific Expression Operators
The JSON
datatype provides these additional SQL operations:
Keyed index operations:
data_table.c.data['some key']
Integer index operations:
data_table.c.data[3]
Path index operations:
data_table.c.data[('key_1', 'key_2', 5, ..., 'key_n')]
Data casters for specific JSON element types, subsequent to an index or path operation being invoked:
data_table.c.data["some key"].as_integer()
New in version 1.3.11.
Additional operations may be available from the dialect-specific versions
of JSON
, such as JSON
and
JSONB
which both offer additional PostgreSQL-specific
operations.
Casting JSON Elements to Other Types
Index operations, i.e. those invoked by calling upon the expression using
the Python bracket operator as in some_column['some key']
, return an
expression object whose type defaults to JSON
by default,
so that
further JSON-oriented instructions may be called upon the result type.
However, it is likely more common that an index operation is expected
to return a specific scalar element, such as a string or integer. In
order to provide access to these elements in a backend-agnostic way,
a series of data casters are provided:
Comparator.as_string()
- return the element as a string
Comparator.as_boolean()
- return the element as a boolean
Comparator.as_float()
- return the element as a float
Comparator.as_integer()
- return the element as an integer
These data casters are implemented by supporting dialects in order to assure that comparisons to the above types will work as expected, such as:
# integer comparison
data_table.c.data["some_integer_key"].as_integer() == 5
# boolean comparison
data_table.c.data["some_boolean"].as_boolean() == True
New in version 1.3.11: Added type-specific casters for the basic JSON data element types.
Note
The data caster functions are new in version 1.3.11, and supersede the previous documented approaches of using CAST; for reference, this looked like:
from sqlalchemy import cast, type_coerce
from sqlalchemy import String, JSON
cast(
data_table.c.data['some_key'], String
) == type_coerce(55, JSON)
The above case now works directly as:
data_table.c.data['some_key'].as_integer() == 5
For details on the previous comparison approach within the 1.3.x series, see the documentation for SQLAlchemy 1.2 or the included HTML files in the doc/ directory of the version’s distribution.
Detecting Changes in JSON columns when using the ORM
The JSON
type, when used with the SQLAlchemy ORM, does not
detect in-place mutations to the structure. In order to detect these, the
sqlalchemy.ext.mutable
extension must be used. This extension will
allow “in-place” changes to the datastructure to produce events which
will be detected by the unit of work. See the example at HSTORE
for a simple example involving a dictionary.
Support for JSON null vs. SQL NULL
When working with NULL values, the JSON
type recommends the
use of two specific constants in order to differentiate between a column
that evaluates to SQL NULL, e.g. no value, vs. the JSON-encoded string
of "null"
. To insert or select against a value that is SQL NULL,
use the constant null()
:
from sqlalchemy import null
conn.execute(table.insert(), json_value=null())
To insert or select against a value that is JSON "null"
, use the
constant JSON.NULL
:
conn.execute(table.insert(), json_value=JSON.NULL)
The JSON
type supports a flag
JSON.none_as_null
which when set to True will result
in the Python constant None
evaluating to the value of SQL
NULL, and when set to False results in the Python constant
None
evaluating to the value of JSON "null"
. The Python
value None
may be used in conjunction with either
JSON.NULL
and null()
in order to indicate NULL
values, but care must be taken as to the value of the
JSON.none_as_null
in these cases.
Customizing the JSON Serializer
The JSON serializer and deserializer used by JSON
defaults to
Python’s json.dumps
and json.loads
functions; in the case of the
psycopg2 dialect, psycopg2 may be using its own custom loader function.
In order to affect the serializer / deserializer, they are currently
configurable at the create_engine()
level via the
create_engine.json_serializer
and
create_engine.json_deserializer
parameters. For example,
to turn off ensure_ascii
:
engine = create_engine(
"sqlite://",
json_serializer=lambda obj: json.dumps(obj, ensure_ascii=False))
Changed in version 1.3.7: SQLite dialect’s json_serializer
and json_deserializer
parameters renamed from _json_serializer
and
_json_deserializer
.
New in version 1.1.
Class signature
class sqlalchemy.types.JSON
(sqlalchemy.types.Indexable
, sqlalchemy.types.TypeEngine
)
Comparator
(expr)¶Define comparison operations for JSON
.
Class signature
class sqlalchemy.types.JSON.Comparator
(sqlalchemy.types.Comparator
, sqlalchemy.types.Comparator
)
sqlalchemy.types.JSON.Comparator.
as_boolean
()¶Cast an indexed value as boolean.
e.g.:
stmt = select([
mytable.c.json_column['some_data'].as_boolean()
]).where(
mytable.c.json_column['some_data'].as_boolean() == True
)
New in version 1.3.11.
sqlalchemy.types.JSON.Comparator.
as_float
()¶Cast an indexed value as float.
e.g.:
stmt = select([
mytable.c.json_column['some_data'].as_float()
]).where(
mytable.c.json_column['some_data'].as_float() == 29.75
)
New in version 1.3.11.
sqlalchemy.types.JSON.Comparator.
as_integer
()¶Cast an indexed value as integer.
e.g.:
stmt = select([
mytable.c.json_column['some_data'].as_integer()
]).where(
mytable.c.json_column['some_data'].as_integer() == 5
)
New in version 1.3.11.
sqlalchemy.types.JSON.Comparator.
as_json
()¶Cast an indexed value as JSON.
This is the default behavior of indexed elements in any case.
Note that comparison of full JSON structures may not be supported by all backends.
New in version 1.3.11.
sqlalchemy.types.JSON.Comparator.
as_string
()¶Cast an indexed value as string.
e.g.:
stmt = select([
mytable.c.json_column['some_data'].as_string()
]).where(
mytable.c.json_column['some_data'].as_string() ==
'some string'
)
New in version 1.3.11.
JSONElementType
¶Common function for index / path elements in a JSON expression.
Class signature
class sqlalchemy.types.JSON.JSONElementType
(sqlalchemy.types.TypeEngine
)
sqlalchemy.types.JSON.JSONElementType.
bind_processor
(dialect)¶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
.
dialect¶ – Dialect instance in use.
sqlalchemy.types.JSON.JSONElementType.
literal_processor
(dialect)¶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.
New in version 0.9.0.
sqlalchemy.types.JSON.JSONElementType.
string_bind_processor
(dialect)¶sqlalchemy.types.JSON.JSONElementType.
string_literal_processor
(dialect)¶JSONIndexType
¶Placeholder for the datatype of a JSON index value.
This allows execution-time processing of JSON index values for special syntaxes.
Class signature
class sqlalchemy.types.JSON.JSONIndexType
(sqlalchemy.types.JSONElementType
)
JSONPathType
¶Placeholder type for JSON path operations.
This allows execution-time processing of a path-based index value into a specific SQL syntax.
Class signature
class sqlalchemy.types.JSON.JSONPathType
(sqlalchemy.types.JSONElementType
)
sqlalchemy.types.JSON.
NULL
= symbol('JSON_NULL')¶Describe the json value of NULL.
This value is used to force the JSON value of "null"
to be
used as the value. A value of Python None
will be recognized
either as SQL NULL or JSON "null"
, based on the setting
of the JSON.none_as_null
flag; the
JSON.NULL
constant can be used to always resolve to JSON "null"
regardless
of this setting. This is in contrast to the null()
construct,
which always resolves to SQL NULL. E.g.:
from sqlalchemy import null
from sqlalchemy.dialects.postgresql import JSON
# will *always* insert SQL NULL
obj1 = MyObject(json_value=null())
# will *always* insert JSON string "null"
obj2 = MyObject(json_value=JSON.NULL)
session.add_all([obj1, obj2])
session.commit()
In order to set JSON NULL as a default value for a column, the most
transparent method is to use text()
:
Table(
'my_table', metadata,
Column('json_data', JSON, default=text("'null'"))
)
While it is possible to use JSON.NULL
in this context, the
JSON.NULL
value will be returned as the value of the
column,
which in the context of the ORM or other repurposing of the default
value, may not be desirable. Using a SQL expression means the value
will be re-fetched from the database within the context of retrieving
generated defaults.
sqlalchemy.types.JSON.
__init__
(none_as_null=False)¶Construct a JSON
type.
none_as_null=False¶ –
if True, persist the value None
as a
SQL NULL value, not the JSON encoding of null
. Note that
when this flag is False, the null()
construct can still
be used to persist a NULL value:
from sqlalchemy import null
conn.execute(table.insert(), data=null())
Note
JSON.none_as_null
does not apply to the
values passed to Column.default
and
Column.server_default
; a value of None
passed for these parameters means “no default present”.
See also
sqlalchemy.types.JSON.
bind_processor
(dialect)¶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
.
dialect¶ – Dialect instance in use.
sqlalchemy.types.JSON.
comparator_factory
¶alias of sqlalchemy.sql.sqltypes.JSON.Comparator
sqlalchemy.types.JSON.
python_type
¶sqlalchemy.types.JSON.
result_processor
(dialect, coltype)¶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
.
sqlalchemy.types.JSON.
should_evaluate_none
¶If True, the Python constant None
is considered to be handled
explicitly by this type.
The ORM uses this flag to indicate that a positive value of None
is passed to the column in an INSERT statement, rather than omitting
the column from the INSERT statement which has the effect of firing
off column-level defaults. It also allows types which have special
behavior for Python None, such as a JSON type, to indicate that
they’d like to handle the None value explicitly.
To set this flag on an existing type, use the
TypeEngine.evaluates_none()
method.
See also
New in version 1.1.
sqlalchemy.types.
INTEGER
¶The SQL INT or INTEGER type.
Class signature
sqlalchemy.types.
NCHAR
(length=None, **kwargs)¶The SQL NCHAR type.
Class signature
sqlalchemy.types.
NVARCHAR
(length=None, **kwargs)¶The SQL NVARCHAR type.
Class signature
sqlalchemy.types.
NUMERIC
(precision=None, scale=None, decimal_return_scale=None, asdecimal=True)¶The SQL NUMERIC type.
Class signature
sqlalchemy.types.
REAL
(precision=None, asdecimal=False, decimal_return_scale=None)¶The SQL REAL type.
Class signature
sqlalchemy.types.
SMALLINT
¶The SQL SMALLINT type.
Class signature
class sqlalchemy.types.SMALLINT
(sqlalchemy.types.SmallInteger
)
sqlalchemy.types.
TEXT
(length=None, collation=None, convert_unicode=False, unicode_error=None, _warn_on_bytestring=False, _expect_unicode=False)¶The SQL TEXT type.
Class signature
sqlalchemy.types.
TIME
(timezone=False)¶The SQL TIME type.
Class signature
sqlalchemy.types.
TIMESTAMP
(timezone=False)¶The SQL TIMESTAMP type.
TIMESTAMP
datatypes have support for timezone
storage on some backends, such as PostgreSQL and Oracle. Use the
TIMESTAMP.timezone
argument in order to enable
“TIMESTAMP WITH TIMEZONE” for these backends.
Class signature
class sqlalchemy.types.TIMESTAMP
(sqlalchemy.types.DateTime
)
sqlalchemy.types.TIMESTAMP.
__init__
(timezone=False)¶Construct a new TIMESTAMP
.
timezone¶ – boolean. Indicates that the TIMESTAMP type should enable timezone support, if available on the target database. On a per-dialect basis is similar to “TIMESTAMP WITH TIMEZONE”. If the target database does not support timezones, this flag is ignored.
sqlalchemy.types.TIMESTAMP.
get_dbapi_type
(dbapi)¶Return the corresponding type object from the underlying DB-API, if any.
This can be useful for calling setinputsizes()
, for example.
sqlalchemy.types.
VARBINARY
(length=None)¶The SQL VARBINARY type.
Class signature
class sqlalchemy.types.VARBINARY
(sqlalchemy.types._Binary
)
sqlalchemy.types.
VARCHAR
(length=None, collation=None, convert_unicode=False, unicode_error=None, _warn_on_bytestring=False, _expect_unicode=False)¶The SQL VARCHAR type.
Class signature
Database-specific types are also available for import from each database’s dialect module. See the Dialects reference for the database you’re interested in.
For example, MySQL has a BIGINT
type and PostgreSQL has an
INET
type. To use these, import them from the module explicitly:
from sqlalchemy.dialects import mysql
table = Table('foo', metadata,
Column('id', mysql.BIGINT),
Column('enumerates', mysql.ENUM('a', 'b', 'c'))
)
Or some PostgreSQL types:
from sqlalchemy.dialects import postgresql
table = Table('foo', metadata,
Column('ipaddress', postgresql.INET),
Column('elements', postgresql.ARRAY(String))
)
Each dialect provides the full set of typenames supported by that backend within its __all__ collection, so that a simple import * or similar will import all supported types as implemented for that backend:
from sqlalchemy.dialects.postgresql import *
t = Table('mytable', metadata,
Column('id', INTEGER, primary_key=True),
Column('name', VARCHAR(300)),
Column('inetaddr', INET)
)
Where above, the INTEGER and VARCHAR types are ultimately from sqlalchemy.types, and INET is specific to the PostgreSQL dialect.
Some dialect level types have the same name as the SQL standard type, but also provide additional arguments. For example, MySQL implements the full range of character and string types including additional arguments such as collation and charset:
from sqlalchemy.dialects.mysql import VARCHAR, TEXT
table = Table('foo', meta,
Column('col1', VARCHAR(200, collation='binary')),
Column('col2', TEXT(charset='latin1'))
)
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