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from types import UnicodeType
def gqn(val):
"""
The geographic quote name function; used for quoting tables and
geometries (they use single rather than the double quotes of the
backend quotename function).
"""
if isinstance(val, basestring):
if isinstance(val, UnicodeType): val = val.encode('ascii')
return "'%s'" % val
else:
return str(val)
class SpatialOperation(object):
"""
Base class for generating spatial SQL.
"""
def __init__(self, function='', operator='', result='', beg_subst='', end_subst=''):
self.function = function
self.operator = operator
self.result = result
self.beg_subst = beg_subst
try:
# Try and put the operator and result into to the
# end substitution.
self.end_subst = end_subst % (operator, result)
except TypeError:
self.end_subst = end_subst
@property
def sql_subst(self):
return ''.join([self.beg_subst, self.end_subst])
def as_sql(self, geo_col):
return self.sql_subst % self.params(geo_col)
def params(self, geo_col):
return (geo_col, self.operator)
class SpatialFunction(SpatialOperation):
"""
Base class for generating spatial SQL related to a function.
"""
def __init__(self, func, beg_subst='%s(%s, %%s', end_subst=')', result='', operator=''):
# Getting the function prefix.
kwargs = {'function' : func, 'operator' : operator, 'result' : result,
'beg_subst' : beg_subst, 'end_subst' : end_subst,}
super(SpatialFunction, self).__init__(**kwargs)
def params(self, geo_col):
return (self.function, geo_col)
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