sqlalchemy.types to_instance Example Code

to_instance is a callable within the sqlalchemy.types module of the SQLAlchemy project.

BOOLEAN, Boolean, DATE, DATETIME, Date, DateTime, Enum, FLOAT, Float, INTEGER, Integer, Interval, NULLTYPE, NullType, String, TEXT, TIME, Text, Time, TypeEngine, and UserDefinedType are several other callables with code examples from the same sqlalchemy.types package.

Example 1 from GeoAlchemy2

GeoAlchemy2 (project documentation and PyPI package information) extends SQLAlchemy with new data types for working with geospatial databases, particularly PostGIS, which is a spatial database extender for PostgreSQL. The project is provided as open source under the MIT license.

GeoAlchemy2 / geoalchemy2 / elements.py

# elements.py
import binascii
import struct

try:
    from sqlalchemy.sql import functions
    from sqlalchemy.sql.functions import FunctionElement
except ImportError:  # SQLA < 0.9  # pragma: no cover
    from sqlalchemy.sql import expression as functions
    from sqlalchemy.sql.expression import FunctionElement
from sqlalchemy.types import to_instance
from sqlalchemy.ext.compiler import compiles

from .compat import PY3, str as str_
from .exc import ArgumentError


if PY3:
    BinasciiError = binascii.Error
else:
    BinasciiError = TypeError


class HasFunction(object):
    pass


class _SpatialElement(HasFunction):

    def __init__(self, data, srid=-1, extended=False):
        self.srid = srid
        self.data = data
        self.extended = extended

    def __str__(self):


## ... source file abbreviated to get to to_instance examples ...


        try:
            bin_data = binascii.unhexlify(data[:114])
        except BinasciiError:
            bin_data = data
            data = str(binascii.hexlify(data).decode(encoding='utf-8'))
        byte_order = bin_data[0]
        srid = bin_data[53:57]
        if not PY3:
            byte_order = bytearray(byte_order)[0]
        srid = struct.unpack('<I' if byte_order else '>I', srid)[0]
        _SpatialElement.__init__(self, data, srid, True)

    @property
    def desc(self):
        return self.data

    @staticmethod
    def _data_from_desc(desc):
        return desc


class CompositeElement(FunctionElement):

    def __init__(self, base, field, type_):
        self.name = field
        self.type = to_instance(type_)

        super(CompositeElement, self).__init__(base)


@compiles(CompositeElement)
def _compile_pgelem(expr, compiler, **kw):
    return '(%s).%s' % (compiler.process(expr.clauses, **kw), expr.name)



## ... source file continues with no further to_instance examples...

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