109 lines
3.8 KiB
Python
109 lines
3.8 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 = [('id', 'in', [1,2,3])]
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>>> expression(e).parse().to_sql()
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'id in (1, 2, 3)'
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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) \
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and element in ['&','|']
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def _is_leaf(self, element):
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return isinstance(element, tuple) \
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and len(element) == 3 \
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and element[1] in ('=', '<>', '<=', '<', '>', '>=', 'like', 'not like', 'ilike', 'not ilike', 'in', 'not in', 'child_of')
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def _is_expression(self, element):
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return isinstance(element, tuple) \
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and len(element) > 2 \
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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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if isinstance(self.right, list):
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self.right = tuple(self.right)
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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 self._is_leaf(self.exp):
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pass
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elif 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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