Types

This module defines the geoalchemy2.types.Geometry, geoalchemy2.types.Geography, and geoalchemy2.types.Raster classes, that are used when defining geometry, geography and raster columns/properties in models.

Reference

class geoalchemy2.types.CompositeType

Bases: sqlalchemy.sql.type_api.UserDefinedType

A wrapper for geoalchemy2.elements.CompositeElement, that can be used as the return type in PostgreSQL functions that return composite values.

This is used as the base class of geoalchemy2.types.GeometryDump.

class comparator_factory(expr)

Bases: sqlalchemy.sql.type_api.TypeEngine.Comparator

typemap = {}

Dictionary used for defining the content types and their corresponding keys. Set in subclasses.

class geoalchemy2.types.Geography(geometry_type='GEOMETRY', srid=- 1, dimension=2, spatial_index=True, use_N_D_index=False, management=False, use_typmod=None, from_text=None, name=None, nullable=True)

Bases: geoalchemy2.types._GISType

The Geography type.

Creating a geography column is done like this:

Column(Geography(geometry_type='POINT', srid=4326))

See geoalchemy2.types._GISType for the list of arguments that can be passed to the constructor.

ElementType

alias of geoalchemy2.elements.WKBElement

as_binary = 'ST_AsBinary'

The “as binary” function to use. Used by the parent class’ column_expression method.

cache_ok = False

Disable cache for this type.

from_text = 'ST_GeogFromText'

The FromText geography constructor. Used by the parent class’ bind_expression method.

name = 'geography'

Type name used for defining geography columns in CREATE TABLE.

class geoalchemy2.types.Geometry(geometry_type='GEOMETRY', srid=- 1, dimension=2, spatial_index=True, use_N_D_index=False, management=False, use_typmod=None, from_text=None, name=None, nullable=True)

Bases: geoalchemy2.types._GISType

The Geometry type.

Creating a geometry column is done like this:

Column(Geometry(geometry_type='POINT', srid=4326))

See geoalchemy2.types._GISType for the list of arguments that can be passed to the constructor.

If srid is set then the WKBElement objects resulting from queries will have that SRID, and, when constructing the WKBElement objects, the SRID won’t be read from the data returned by the database. If srid is not set (meaning it’s -1) then the SRID set in WKBElement objects will be read from the data returned by the database.

ElementType

alias of geoalchemy2.elements.WKBElement

as_binary = 'ST_AsEWKB'

The “as binary” function to use. Used by the parent class’ column_expression method.

cache_ok = False

Disable cache for this type.

from_text = 'ST_GeomFromEWKT'

The “from text” geometry constructor. Used by the parent class’ bind_expression method.

name = 'geometry'

Type name used for defining geometry columns in CREATE TABLE.

class geoalchemy2.types.GeometryDump

Bases: geoalchemy2.types.CompositeType

The return type for functions like ST_Dump, consisting of a path and a geom field. You should normally never use this class directly.

cache_ok = True

Enable cache for this type.

typemap = {'geom': <class 'geoalchemy2.types.Geometry'>, 'path': ARRAY(Integer())}

Dictionary defining the contents of a geometry_dump.

class geoalchemy2.types.Raster(*args, **kwargs)

Bases: geoalchemy2.types._GISType

The Raster column type.

Creating a raster column is done like this:

Column(Raster)

This class defines the result_processor method, so that raster values received from the database are converted to geoalchemy2.elements.RasterElement objects.

Constructor arguments:

spatial_index

Indicate if a spatial index should be created. Default is True.

ElementType

alias of geoalchemy2.elements.RasterElement

as_binary = 'raster'

The “as binary” function to use. Used by the parent class’ column_expression method.

cache_ok = False

Disable cache for this type.

comparator_factory

alias of geoalchemy2.comparator.BaseComparator

from_text = 'raster'

The “from text” raster constructor. Used by the parent class’ bind_expression method.

name = 'raster'

Type name used for defining raster columns in CREATE TABLE.

class geoalchemy2.types.SummaryStats

Bases: geoalchemy2.types.CompositeType

Define the composite type returned by the function ST_SummaryStatsAgg

cache_ok = True

Enable cache for this type.

class geoalchemy2.types._GISType(geometry_type='GEOMETRY', srid=- 1, dimension=2, spatial_index=True, use_N_D_index=False, management=False, use_typmod=None, from_text=None, name=None, nullable=True)

Bases: sqlalchemy.sql.type_api.UserDefinedType

The base class for geoalchemy2.types.Geometry and geoalchemy2.types.Geography.

This class defines bind_expression and column_expression methods that wrap column expressions in ST_GeomFromEWKT, ST_GeogFromText, or ST_AsEWKB calls.

This class also defines result_processor and bind_processor methods. The function returned by result_processor converts WKB values received from the database to geoalchemy2.elements.WKBElement objects. The function returned by bind_processor converts geoalchemy2.elements.WKTElement objects to EWKT strings.

Constructor arguments:

geometry_type

The geometry type.

Possible values are:

• "GEOMETRY",

• "POINT",

• "LINESTRING",

• "POLYGON",

• "MULTIPOINT",

• "MULTILINESTRING",

• "MULTIPOLYGON",

• "GEOMETRYCOLLECTION",

• "CURVE",

• None.

The latter is actually not supported with geoalchemy2.types.Geography.

When set to None then no “geometry type” constraints will be attached to the geometry type declaration. Using None here is not compatible with setting management to True.

Default is "GEOMETRY".

srid

The SRID for this column. E.g. 4326. Default is -1.

dimension

The dimension of the geometry. Default is 2.

With management set to True, that is when AddGeometryColumn is used to add the geometry column, there are two constraints:

• The geometry_type must not end with "ZM". This is due to PostGIS’ AddGeometryColumn failing with ZM geometry types. Instead the “simple” geometry type (e.g. POINT rather POINTZM) should be used with dimension set to 4.

• When the geometry_type ends with "Z" or "M" then dimension must be set to 3.

With management set to False (the default) dimension is not taken into account, and the actual dimension is fully defined with the geometry_type.

spatial_index

Indicate if a spatial index should be created. Default is True.

use_N_D_index

Use the N-D index instead of the standard 2-D index.

management

Indicate if the AddGeometryColumn and DropGeometryColumn managements functions should be called when adding and dropping the geometry column. Should be set to True for PostGIS 1.x. Default is False. Note that this option has no effect for geoalchemy2.types.Geography.

use_typmod

By default PostgreSQL type modifiers are used to create the geometry column. To use check constraints instead set use_typmod to False. By default this option is not included in the call to AddGeometryColumn. Note that this option is only taken into account if management is set to True and is only available for PostGIS 2.x.

as_binary = None

The name of the “as binary” function for this type. Set in subclasses.

bind_expression(bindvalue)

Specific bind_expression that automatically adds a conversion function

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.

Parameters

dialect – Dialect instance in use.

cache_ok = False

Disable cache for this type.

column_expression(col)

Specific column_expression that automatically adds a conversion function

comparator_factory

alias of geoalchemy2.comparator.Comparator

from_text = None

The name of “from text” function for this type. Set in subclasses.

name = None

Name used for defining the main geo type (geometry or geography) in CREATE TABLE statements. Set in subclasses.

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.

Parameters

• dialect – Dialect instance in use.

• coltype – DBAPI coltype argument received in cursor.description.