text: import re
  from decimal import Decimal
  
  from django.contrib.gis.db.backends.base import BaseSpatialOperations
  from django.contrib.gis.db.backends.util import SpatialOperation, SpatialFunction
  from django.contrib.gis.db.backends.spatialite.adapter import SpatiaLiteAdapter
  from django.contrib.gis.geometry.backend import Geometry
  from django.contrib.gis.measure import Distance
  from django.core.exceptions import ImproperlyConfigured
  from django.db.backends.sqlite3.base import DatabaseOperations
  from django.db.utils import DatabaseError
  from django.utils import six
  from django.utils.functional import cached_property
  
  
  class SpatiaLiteOperator(SpatialOperation):
      "For SpatiaLite operators (e.g. `&&`, `~`)."
      def __init__(self, operator):
          super(SpatiaLiteOperator, self).__init__(operator=operator)
  
  class SpatiaLiteFunction(SpatialFunction):
      "For SpatiaLite function calls."
      def __init__(self, function, **kwargs):
          super(SpatiaLiteFunction, self).__init__(function, **kwargs)
  
  class SpatiaLiteFunctionParam(SpatiaLiteFunction):
      "For SpatiaLite functions that take another parameter."
      sql_template = '%(function)s(%(geo_col)s, %(geometry)s, %%s)'
  
  class SpatiaLiteDistance(SpatiaLiteFunction):
      "For SpatiaLite distance operations."
      dist_func = 'Distance'
      sql_template = '%(function)s(%(geo_col)s, %(geometry)s) %(operator)s %%s'
  
      def __init__(self, operator):
          super(SpatiaLiteDistance, self).__init__(self.dist_func,
                                                   operator=operator)
  
  class SpatiaLiteRelate(SpatiaLiteFunctionParam):
      "For SpatiaLite Relate(<geom>, <pattern>) calls."
      pattern_regex = re.compile(r'^[012TF\*]{9}$')
      def __init__(self, pattern):
          if not self.pattern_regex.match(pattern):
              raise ValueError('Invalid intersection matrix pattern "%s".' % pattern)
          super(SpatiaLiteRelate, self).__init__('Relate')
  
  # Valid distance types and substitutions
  dtypes = (Decimal, Distance, float) + six.integer_types
  def get_dist_ops(operator):
      "Returns operations for regular distances; spherical distances are not currently supported."
      return (SpatiaLiteDistance(operator),)
  
  class SpatiaLiteOperations(DatabaseOperations, BaseSpatialOperations):
      compiler_module = 'django.contrib.gis.db.models.sql.compiler'
      name = 'spatialite'
      spatialite = True
      version_regex = re.compile(r'^(?P<major>\d)\.(?P<minor1>\d)\.(?P<minor2>\d+)')
      valid_aggregates = dict([(k, None) for k in ('Extent', 'Union')])
  
      Adapter = SpatiaLiteAdapter
      Adaptor = Adapter # Backwards-compatibility alias.
  
      area = 'Area'
      centroid = 'Centroid'
      contained = 'MbrWithin'
      difference = 'Difference'
      distance = 'Distance'
      envelope = 'Envelope'
      intersection = 'Intersection'
      length = 'GLength' # OpenGis defines Length, but this conflicts with an SQLite reserved keyword
      num_geom = 'NumGeometries'
      num_points = 'NumPoints'
      point_on_surface = 'PointOnSurface'
      scale = 'ScaleCoords'
      svg = 'AsSVG'
      sym_difference = 'SymDifference'
      transform = 'Transform'
      translate = 'ShiftCoords'
      union = 'GUnion' # OpenGis defines Union, but this conflicts with an SQLite reserved keyword
      unionagg = 'GUnion'
  
      from_text = 'GeomFromText'
      from_wkb = 'GeomFromWKB'
      select = 'AsText(%s)'
  
      geometry_functions = {
          'equals' : SpatiaLiteFunction('Equals'),
          'disjoint' : SpatiaLiteFunction('Disjoint'),
          'touches' : SpatiaLiteFunction('Touches'),
          'crosses' : SpatiaLiteFunction('Crosses'),
          'within' : SpatiaLiteFunction('Within'),
          'overlaps' : SpatiaLiteFunction('Overlaps'),
          'contains' : SpatiaLiteFunction('Contains'),
          'intersects' : SpatiaLiteFunction('Intersects'),
          'relate' : (SpatiaLiteRelate, six.string_types),
          # Returns true if B's bounding box completely contains A's bounding box.
          'contained' : SpatiaLiteFunction('MbrWithin'),
          # Returns true if A's bounding box completely contains B's bounding box.
          'bbcontains' : SpatiaLiteFunction('MbrContains'),
          # Returns true if A's bounding box overlaps B's bounding box.
          'bboverlaps' : SpatiaLiteFunction('MbrOverlaps'),
          # These are implemented here as synonyms for Equals
          'same_as' : SpatiaLiteFunction('Equals'),
          'exact' : SpatiaLiteFunction('Equals'),
          }
  
      distance_functions = {
          'distance_gt' : (get_dist_ops('>'), dtypes),
          'distance_gte' : (get_dist_ops('>='), dtypes),
          'distance_lt' : (get_dist_ops('<'), dtypes),
          'distance_lte' : (get_dist_ops('<='), dtypes),
          }
      geometry_functions.update(distance_functions)
  
      def __init__(self, connection):
          super(DatabaseOperations, self).__init__(connection)
  
          # Creating the GIS terms dictionary.
          gis_terms = ['isnull']
          gis_terms += self.geometry_functions.keys()
          self.gis_terms = dict([(term, None) for term in gis_terms])
  
      @cached_property
      def spatial_version(self):
          """Determine the version of the SpatiaLite library."""
          try:
              version = self.spatialite_version_tuple()[1:]
          except Exception as msg:
              raise ImproperlyConfigured('Cannot determine the SpatiaLite version for the "%s" '
                                         'database (error was "%s").  Was the SpatiaLite initialization '
                                         'SQL loaded on this database?' %
                                         (self.connection.settings_dict['NAME'], msg))
          if version < (2, 3, 0):
              raise ImproperlyConfigured('GeoDjango only supports SpatiaLite versions '
                                         '2.3.0 and above')
          return version
  
      @property
      def _version_greater_2_4_0_rc4(self):
          if self.spatial_version >= (2, 4, 1):
              return True
          elif self.spatial_version < (2, 4, 0):
              return False
          else:
              # Spatialite 2.4.0-RC4 added AsGML and AsKML, however both
              # RC2 (shipped in popular Debian/Ubuntu packages) and RC4
              # report version as '2.4.0', so we fall back to feature detection
              try:
                  self._get_spatialite_func("AsGML(GeomFromText('POINT(1 1)'))")
              except DatabaseError:
                  return False
              return True
  
      @cached_property
      def gml(self):
          return 'AsGML' if self._version_greater_2_4_0_rc4 else None
  
      @cached_property
      def kml(self):
          return 'AsKML' if self._version_greater_2_4_0_rc4 else None
  
      @cached_property
      def geojson(self):
          return 'AsGeoJSON' if self.spatial_version >= (3, 0, 0) else None
  
      def check_aggregate_support(self, aggregate):
          """
          Checks if the given aggregate name is supported (that is, if it's
          in `self.valid_aggregates`).
          """
          agg_name = aggregate.__class__.__name__
          return agg_name in self.valid_aggregates
  
      def convert_geom(self, wkt, geo_field):
          """
          Converts geometry WKT returned from a SpatiaLite aggregate.
          """
          if wkt:
              return Geometry(wkt, geo_field.srid)
          else:
              return None
  
      def geo_db_type(self, f):
          """
          Returns None because geometry columnas are added via the
          `AddGeometryColumn` stored procedure on SpatiaLite.
          """
          return None
  
      def get_distance(self, f, value, lookup_type):
          """
          Returns the distance parameters for the given geometry field,
          lookup value, and lookup type.  SpatiaLite only supports regular
          cartesian-based queries (no spheroid/sphere calculations for point
          geometries like PostGIS).
          """
          if not value:
              return []
          value = value[0]
          if isinstance(value, Distance):
              if f.geodetic(self.connection):
                  raise ValueError('SpatiaLite does not support distance queries on '
                                   'geometry fields with a geodetic coordinate system. '
                                   'Distance objects; use a numeric value of your '
                                   'distance in degrees instead.')
              else:
                  dist_param = getattr(value, Distance.unit_attname(f.units_name(self.connection)))
          else:
              dist_param = value
          return [dist_param]
  
      def get_geom_placeholder(self, f, value):
          """
          Provides a proper substitution value for Geometries that are not in the
          SRID of the field.  Specifically, this routine will substitute in the
          Transform() and GeomFromText() function call(s).
          """
          def transform_value(value, srid):
              return not (value is None or value.srid == srid)
          if hasattr(value, 'expression'):
              if transform_value(value, f.srid):
                  placeholder = '%s(%%s, %s)' % (self.transform, f.srid)
              else:
                  placeholder = '%s'
              # No geometry value used for F expression, substitue in
              # the column name instead.
              return placeholder % self.get_expression_column(value)
          else:
              if transform_value(value, f.srid):
                  # Adding Transform() to the SQL placeholder.
                  return '%s(%s(%%s,%s), %s)' % (self.transform, self.from_text, value.srid, f.srid)
              else:
                  return '%s(%%s,%s)' % (self.from_text, f.srid)
  
      def _get_spatialite_func(self, func):
          """
          Helper routine for calling SpatiaLite functions and returning
          their result.
          """
          cursor = self.connection._cursor()
          try:
              try:
                  cursor.execute('SELECT %s' % func)
                  row = cursor.fetchone()
              except:
                  # Responsibility of caller to perform error handling.
                  raise
          finally:
              cursor.close()
          return row[0]
  
      def geos_version(self):
          "Returns the version of GEOS used by SpatiaLite as a string."
          return self._get_spatialite_func('geos_version()')
  
      def proj4_version(self):
          "Returns the version of the PROJ.4 library used by SpatiaLite."
          return self._get_spatialite_func('proj4_version()')
  
      def spatialite_version(self):
          "Returns the SpatiaLite library version as a string."
          return self._get_spatialite_func('spatialite_version()')
  
      def spatialite_version_tuple(self):
          """
          Returns the SpatiaLite version as a tuple (version string, major,
          minor, subminor).
          """
          # Getting the SpatiaLite version.
          try:
              version = self.spatialite_version()
          except DatabaseError:
              # The `spatialite_version` function first appeared in version 2.3.1
              # of SpatiaLite, so doing a fallback test for 2.3.0 (which is
              # used by popular Debian/Ubuntu packages).
              version = None
              try:
                  tmp = self._get_spatialite_func("X(GeomFromText('POINT(1 1)'))")
                  if tmp == 1.0: version = '2.3.0'
              except DatabaseError:
                  pass
              # If no version string defined, then just re-raise the original
              # exception.
              if version is None: raise
  
          m = self.version_regex.match(version)
          if m:
              major = int(m.group('major'))
              minor1 = int(m.group('minor1'))
              minor2 = int(m.group('minor2'))
          else:
              raise Exception('Could not parse SpatiaLite version string: %s' % version)
  
          return (version, major, minor1, minor2)
  
      def spatial_aggregate_sql(self, agg):
          """
          Returns the spatial aggregate SQL template and function for the
          given Aggregate instance.
          """
          agg_name = agg.__class__.__name__
          if not self.check_aggregate_support(agg):
              raise NotImplementedError('%s spatial aggregate is not implmented for this backend.' % agg_name)
          agg_name = agg_name.lower()
          if agg_name == 'union': agg_name += 'agg'
          sql_template = self.select % '%(function)s(%(field)s)'
          sql_function = getattr(self, agg_name)
          return sql_template, sql_function
  
      def spatial_lookup_sql(self, lvalue, lookup_type, value, field, qn):
          """
          Returns the SpatiaLite-specific SQL for the given lookup value
          [a tuple of (alias, column, db_type)], lookup type, lookup
          value, the model field, and the quoting function.
          """
          alias, col, db_type = lvalue
  
          # Getting the quoted field as `geo_col`.
          geo_col = '%s.%s' % (qn(alias), qn(col))
  
          if lookup_type in self.geometry_functions:
              # See if a SpatiaLite geometry function matches the lookup type.
              tmp = self.geometry_functions[lookup_type]
  
              # Lookup types that are tuples take tuple arguments, e.g., 'relate' and
              # distance lookups.
              if isinstance(tmp, tuple):
                  # First element of tuple is the SpatiaLiteOperation instance, and the
                  # second element is either the type or a tuple of acceptable types
                  # that may passed in as further parameters for the lookup type.
                  op, arg_type = tmp
  
                  # Ensuring that a tuple _value_ was passed in from the user
                  if not isinstance(value, (tuple, list)):
                      raise ValueError('Tuple required for `%s` lookup type.' % lookup_type)
  
                  # Geometry is first element of lookup tuple.
                  geom = value[0]
  
                  # Number of valid tuple parameters depends on the lookup type.
                  if len(value) != 2:
                      raise ValueError('Incorrect number of parameters given for `%s` lookup type.' % lookup_type)
  
                  # Ensuring the argument type matches what we expect.
                  if not isinstance(value[1], arg_type):
                      raise ValueError('Argument type should be %s, got %s instead.' % (arg_type, type(value[1])))
  
                  # For lookup type `relate`, the op instance is not yet created (has
                  # to be instantiated here to check the pattern parameter).
                  if lookup_type == 'relate':
                      op = op(value[1])
                  elif lookup_type in self.distance_functions:
                      op = op[0]
              else:
                  op = tmp
                  geom = value
              # Calling the `as_sql` function on the operation instance.
              return op.as_sql(geo_col, self.get_geom_placeholder(field, geom))
          elif lookup_type == 'isnull':
              # Handling 'isnull' lookup type
              return "%s IS %sNULL" % (geo_col, ('' if value else 'NOT ')), []
  
          raise TypeError("Got invalid lookup_type: %s" % repr(lookup_type))
  
      # Routines for getting the OGC-compliant models.
      def geometry_columns(self):
          from django.contrib.gis.db.backends.spatialite.models import GeometryColumns
          return GeometryColumns
  
      def spatial_ref_sys(self):
          from django.contrib.gis.db.backends.spatialite.models import SpatialRefSys
          return SpatialRefSys
  