96 lines
3.6 KiB
Python
96 lines
3.6 KiB
Python
#!/usr/bin/env python
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# -*- encoding: utf-8 -*-
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class expression( object ):
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"""
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parse a domain expression
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examples:
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>>> e = [('foo', '=', 'bar')]
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>>> expression(e).parse().to_sql()
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'foo = bar'
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>>> e = [('field', '=', 'value'), ('field', '!=', 'value')]
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>>> expression(e).parse().to_sql()
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'( field = value AND field != value )'
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>>> e = [('&', ('field', '<', 'value'), ('field', '>', 'value'))]
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>>> expression(e).parse().to_sql()
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'( field < value AND field > value )'
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>>> e = [('|', ('field', '=', 'value'), ('field', '=', 'value'))]
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>>> expression(e).parse().to_sql()
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'( field = value OR field = value )'
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>>> e = [('&', ('field1', '=', 'value'), ('field2', '=', 'value'), ('|', ('field3', '<>', 'value'), ('field4', '=', 'value')))]
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>>> expression(e).parse().to_sql()
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'( field1 = value AND field2 = value AND ( field3 <> value OR field4 = value ) )'
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>>> e = [('&', ('|', ('a', '=', '1'), ('b', '=', '2')), ('|', ('c', '=', '3'), ('d', '=', '4')))]
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>>> expression(e).parse().to_sql()
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'( ( a = 1 OR b = 2 ) AND ( c = 3 OR d = 4 ) )'
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>>> e = [('|', (('a', '=', '1'), ('b', '=', '2')), (('c', '=', '3'), ('d', '=', '4')))]
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>>> expression(e).parse().to_sql()
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'( ( a = 1 AND b = 2 ) OR ( c = 3 AND d = 4 ) )'
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>>> expression('fail').parse().to_sql()
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Traceback (most recent call last):
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...
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ValueError: Bad expression: 'fail'
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>>> e = [('fail', 'is', 'True')]
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>>> expression(e).parse().to_sql()
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Traceback (most recent call last):
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...
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ValueError: Bad expression: ('&', ('fail', 'is', 'True'))
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"""
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def _is_operator( self, element ):
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return isinstance( element, str ) and element in ['&','|']
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def _is_leaf( self, element ):
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return isinstance( element, tuple ) and len( element ) == 3 and element[1] in ['=', '<>', '!=', '<=', '<', '>', '>=', 'like', 'not like', 'ilike', 'not ilike']
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def _is_expression( self, element ):
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return isinstance( element, tuple ) and len( element ) > 2 and self._is_operator( element[0] )
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def __init__( self, exp ):
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if isinstance( exp, tuple ):
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if not self._is_leaf( exp ) and not self._is_operator( exp[0] ):
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exp = list( exp )
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if isinstance( exp, list ):
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if len( exp ) == 1 and self._is_leaf( exp[0] ):
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exp = exp[0]
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else:
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if not self._is_operator( exp[0][0] ):
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exp.insert( 0, '&' )
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exp = tuple( exp )
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else:
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exp = exp[0]
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self.exp = exp
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self.operator = '&'
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self.children = []
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self.left, self.right = None, None
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if self._is_leaf(self.exp):
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self.left, self.operator, self.right = self.exp
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elif not self._is_expression( self.exp ):
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raise ValueError, 'Bad expression: %r' % (self.exp,)
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def parse( self ):
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if not self._is_leaf( self.exp ) and self._is_expression( self.exp ):
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self.operator = self.exp[0]
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for element in self.exp[1:]:
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if not self._is_operator( element ):
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self.children.append( expression(element).parse() )
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return self
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def to_sql( self ):
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if self._is_leaf( self.exp ):
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return "%s %s %s" % ( self.left, self.operator, self.right )
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else:
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return "( %s )" % (" %s " % {'&' : 'AND', '|' : 'OR' }[self.operator]).join([child.to_sql() for child in self.children])
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if __name__ == '__main__':
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import doctest
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doctest.testmod()
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# vim:expandtab:smartindent:tabstop=4:softtabstop=4:shiftwidth=4:
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