2 # -*- encoding: utf-8 -*-
4 class expression( object ):
6 parse a domain expression
9 >>> e = [('foo', '=', 'bar')]
10 >>> expression(e).parse().to_sql()
12 >>> e = [('field', '=', 'value'), ('field', '!=', 'value')]
13 >>> expression(e).parse().to_sql()
14 '( field = value AND field != value )'
15 >>> e = [('&', ('field', '<', 'value'), ('field', '>', 'value'))]
16 >>> expression(e).parse().to_sql()
17 '( field < value AND field > value )'
18 >>> e = [('|', ('field', '=', 'value'), ('field', '=', 'value'))]
19 >>> expression(e).parse().to_sql()
20 '( field = value OR field = value )'
21 >>> e = [('&', ('field1', '=', 'value'), ('field2', '=', 'value'), ('|', ('field3', '<>', 'value'), ('field4', '=', 'value')))]
22 >>> expression(e).parse().to_sql()
23 '( field1 = value AND field2 = value AND ( field3 <> value OR field4 = value ) )'
24 >>> e = [('&', ('|', ('a', '=', '1'), ('b', '=', '2')), ('|', ('c', '=', '3'), ('d', '=', '4')))]
25 >>> expression(e).parse().to_sql()
26 '( ( a = 1 OR b = 2 ) AND ( c = 3 OR d = 4 ) )'
27 >>> e = [('|', (('a', '=', '1'), ('b', '=', '2')), (('c', '=', '3'), ('d', '=', '4')))]
28 >>> expression(e).parse().to_sql()
29 '( ( a = 1 AND b = 2 ) OR ( c = 3 AND d = 4 ) )'
30 >>> expression('fail').parse().to_sql()
31 Traceback (most recent call last):
33 ValueError: Bad expression: 'fail'
34 >>> e = [('fail', 'is', 'True')]
35 >>> expression(e).parse().to_sql()
36 Traceback (most recent call last):
38 ValueError: Bad expression: ('&', ('fail', 'is', 'True'))
41 def _is_operator( self, element ):
42 return isinstance( element, str ) and element in ['&','|']
44 def _is_leaf( self, element ):
45 return isinstance( element, tuple ) and len( element ) == 3 and element[1] in ['=', '<>', '!=', '<=', '<', '>', '>=', 'like', 'not like', 'ilike', 'not ilike']
47 def _is_expression( self, element ):
48 return isinstance( element, tuple ) and len( element ) > 2 and self._is_operator( element[0] )
50 def __init__( self, exp ):
51 if isinstance( exp, tuple ):
52 if not self._is_leaf( exp ) and not self._is_operator( exp[0] ):
54 if isinstance( exp, list ):
55 if len( exp ) == 1 and self._is_leaf( exp[0] ):
58 if not self._is_operator( exp[0][0] ):
68 self.left, self.right = None, None
69 if self._is_leaf(self.exp):
70 self.left, self.operator, self.right = self.exp
71 elif not self._is_expression( self.exp ):
72 raise ValueError, 'Bad expression: %r' % (self.exp,)
75 if not self._is_leaf( self.exp ) and self._is_expression( self.exp ):
76 self.operator = self.exp[0]
78 for element in self.exp[1:]:
79 if not self._is_operator( element ):
80 self.children.append( expression(element).parse() )
84 if self._is_leaf( self.exp ):
85 return "%s %s %s" % ( self.left, self.operator, self.right )
87 return "( %s )" % (" %s " % {'&' : 'AND', '|' : 'OR' }[self.operator]).join([child.to_sql() for child in self.children])
90 if __name__ == '__main__':
94 # vim:expandtab:smartindent:tabstop=4:softtabstop=4:shiftwidth=4: