Construye la expresion

def result(self):
        """
        Construye la expresion
        """ 
        
        field = re.sub(REGEX_CLEANER, '', self.field)

        try:
            value = float(self.value)
        except TypeError:
        	value = "(%s)" % ( "', '".join(self.value) )
        except ValueError:
            value = str(self.value) \
                .replace("\\", r"\\") \
                .replace('"', r'\"') \
                .replace("'", r"\'")

            value = "'%s'" % value
        
        res = "%s %s %s" % (field, self.operator, value)

        if self.conjunction:
            res = "%s %s" % (self.conjunction, res)
        
        return res