pattern query

query.py

from django.utils import tree

PATTERN_DICT = {
    "ALPHABET": r"a-zA-Z",
    "NUMBER": r"0-9",
}

class S(tree.Node):
    """

    """
    # Connection types
    AND = 'AND'
    #OR = 'OR'
    default = AND

    def __init__(self, *args, **kwargs):
        super(S, self).__init__(children=list(args) + kwargs.items())

    def _combine(self, other, conn):
        if not isinstance(other, S):
            raise TypeError(other)
        obj = type(self)()
        obj.add(self, conn)
        obj.add(other, conn)
        return obj

    def __or__(self, other):
        return self._combine(other, self.AND)

    def __and__(self, other):
        return self._combine(other, self.AND)
        

ALPHABET = S("ALPHABET")
NUMBER = S("NUMBER")

def regex_from_S(s):
    """
    >>> regex_from_S(ALPHABET)
    '[a-z-A-Z]+'

    >>> regex_from_S(ALPHABET&NUMBER)
    '[a-z-A-Z0-9]+'
    """
    
    if isinstance(s, S):
        if s.connector == "AND":
            return "[%s]+" % (r"".join([regex_from_S(c) for c in s.children]),)
        else:
            raise ValueError
    elif isinstance(s, basestring):
        return PATTERN_DICT[s]
    else:
        raise TypeError