234 lines
8.0 KiB
Python
234 lines
8.0 KiB
Python
"""
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Imports the SpatialRefSys and GeometryColumns models dependent on the
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spatial database backend.
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"""
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import re
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from django.conf import settings
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# Checking for the presence of GDAL (needed for the SpatialReference object)
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from django.contrib.gis.gdal import HAS_GDAL, PYTHON23
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if HAS_GDAL:
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from django.contrib.gis.gdal import SpatialReference
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class SpatialRefSysMixin(object):
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"""
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The SpatialRefSysMixin is a class used by the database-dependent
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SpatialRefSys objects to reduce redundnant code.
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"""
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# For pulling out the spheroid from the spatial reference string. This
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# regular expression is used only if the user does not have GDAL installed.
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# TODO: Flattening not used in all ellipsoids, could also be a minor axis,
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# or 'b' parameter.
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spheroid_regex = re.compile(r'.+SPHEROID\[\"(?P<name>.+)\",(?P<major>\d+(\.\d+)?),(?P<flattening>\d{3}\.\d+),')
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# For pulling out the units on platforms w/o GDAL installed.
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# TODO: Figure out how to pull out angular units of projected coordinate system and
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# fix for LOCAL_CS types. GDAL should be highly recommended for performing
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# distance queries.
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units_regex = re.compile(r'.+UNIT ?\["(?P<unit_name>[\w \'\(\)]+)", ?(?P<unit>[\d\.]+)(,AUTHORITY\["(?P<unit_auth_name>[\w \'\(\)]+)","(?P<unit_auth_val>\d+)"\])?\]([\w ]+)?(,AUTHORITY\["(?P<auth_name>[\w \'\(\)]+)","(?P<auth_val>\d+)"\])?\]$')
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def srs(self):
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"""
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Returns a GDAL SpatialReference object, if GDAL is installed.
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"""
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if HAS_GDAL:
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# TODO: Is caching really necessary here? Is complexity worth it?
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if hasattr(self, '_srs'):
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# Returning a clone of the cached SpatialReference object.
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return self._srs.clone()
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else:
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# Attempting to cache a SpatialReference object.
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# Trying to get from WKT first.
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try:
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self._srs = SpatialReference(self.wkt)
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return self.srs
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except Exception, msg:
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pass
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try:
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self._srs = SpatialReference(self.proj4text)
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return self.srs
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except Exception, msg:
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pass
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raise Exception('Could not get OSR SpatialReference from WKT: %s\nError:\n%s' % (self.wkt, msg))
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else:
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raise Exception('GDAL is not installed.')
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srs = property(srs)
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def ellipsoid(self):
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"""
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Returns a tuple of the ellipsoid parameters:
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(semimajor axis, semiminor axis, and inverse flattening).
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"""
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if HAS_GDAL:
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return self.srs.ellipsoid
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else:
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m = self.spheroid_regex.match(self.wkt)
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if m: return (float(m.group('major')), float(m.group('flattening')))
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else: return None
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ellipsoid = property(ellipsoid)
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def name(self):
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"Returns the projection name."
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return self.srs.name
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name = property(name)
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def spheroid(self):
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"Returns the spheroid name for this spatial reference."
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return self.srs['spheroid']
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spheroid = property(spheroid)
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def datum(self):
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"Returns the datum for this spatial reference."
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return self.srs['datum']
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datum = property(datum)
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def projected(self):
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"Is this Spatial Reference projected?"
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if HAS_GDAL:
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return self.srs.projected
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else:
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return self.wkt.startswith('PROJCS')
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projected = property(projected)
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def local(self):
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"Is this Spatial Reference local?"
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if HAS_GDAL:
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return self.srs.local
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else:
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return self.wkt.startswith('LOCAL_CS')
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local = property(local)
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def geographic(self):
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"Is this Spatial Reference geographic?"
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if HAS_GDAL:
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return self.srs.geographic
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else:
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return self.wkt.startswith('GEOGCS')
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geographic = property(geographic)
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def linear_name(self):
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"Returns the linear units name."
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if HAS_GDAL:
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return self.srs.linear_name
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elif self.geographic:
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return None
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else:
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m = self.units_regex.match(self.wkt)
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return m.group('unit_name')
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linear_name = property(linear_name)
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def linear_units(self):
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"Returns the linear units."
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if HAS_GDAL:
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return self.srs.linear_units
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elif self.geographic:
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return None
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else:
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m = self.units_regex.match(self.wkt)
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return m.group('unit')
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linear_units = property(linear_units)
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def angular_name(self):
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"Returns the name of the angular units."
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if HAS_GDAL:
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return self.srs.angular_name
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elif self.projected:
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return None
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else:
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m = self.units_regex.match(self.wkt)
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return m.group('unit_name')
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angular_name = property(angular_name)
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def angular_units(self):
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"Returns the angular units."
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if HAS_GDAL:
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return self.srs.angular_units
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elif self.projected:
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return None
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else:
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m = self.units_regex.match(self.wkt)
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return m.group('unit')
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angular_units = property(angular_units)
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def units(self):
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"Returns a tuple of the units and the name."
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if self.projected or self.local:
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return (self.linear_units, self.linear_name)
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elif self.geographic:
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return (self.angular_units, self.angular_name)
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else:
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return (None, None)
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units = property(units)
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def get_units(cls, wkt):
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"""
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Class method used by GeometryField on initialization to
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retrive the units on the given WKT, without having to use
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any of the database fields.
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"""
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if HAS_GDAL:
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return SpatialReference(wkt).units
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else:
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m = cls.units_regex.match(wkt)
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return m.group('unit'), m.group('unit_name')
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get_units = classmethod(get_units)
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def get_spheroid(cls, wkt, string=True):
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"""
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Class method used by GeometryField on initialization to
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retrieve the `SPHEROID[..]` parameters from the given WKT.
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"""
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if HAS_GDAL:
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srs = SpatialReference(wkt)
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sphere_params = srs.ellipsoid
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sphere_name = srs['spheroid']
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else:
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m = cls.spheroid_regex.match(wkt)
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if m:
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sphere_params = (float(m.group('major')), float(m.group('flattening')))
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sphere_name = m.group('name')
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else:
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return None
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if not string:
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return sphere_name, sphere_params
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else:
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# `string` parameter used to place in format acceptable by PostGIS
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if len(sphere_params) == 3:
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radius, flattening = sphere_params[0], sphere_params[2]
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else:
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radius, flattening = sphere_params
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return 'SPHEROID["%s",%s,%s]' % (sphere_name, radius, flattening)
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get_spheroid = classmethod(get_spheroid)
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def __unicode__(self):
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"""
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Returns the string representation. If GDAL is installed,
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it will be 'pretty' OGC WKT.
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"""
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try:
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return unicode(self.srs)
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except:
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return unicode(self.wkt)
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# Django test suite on 2.3 platforms will choke on code inside this
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# conditional.
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if not PYTHON23:
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try:
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# try/except'ing the importation of SpatialBackend. Have to fail
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# silently because this module may be inadvertently invoked by
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# non-GeoDjango users (e.g., when the Django test suite executes
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# the models.py of all contrib apps).
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from django.contrib.gis.db.backend import SpatialBackend
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if SpatialBackend.mysql: raise Exception
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# Exposing the SpatialRefSys and GeometryColumns models.
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class SpatialRefSys(SpatialBackend.SpatialRefSys, SpatialRefSysMixin):
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pass
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GeometryColumns = SpatialBackend.GeometryColumns
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except:
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pass
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