ahaha.py

def func_environment():
    env = dict()
    def symbol(identify, bp=0, auto_commit = True):
        try:
            s = env[identify]
        except Exception:
            class s(Token):
                pass
            if auto_commit:
                s.__name__  = 'symbol-{}'.format(identify)
                s.id = identify
                s.lbp = bp
                env[identify] = s
            else:
                s = None
        else:
            s.lbp = max(s.lbp, bp)
        return s
    return symbol


class environment(object):
    def __init__(self, parent=None):
        self.env = dict()
        self.parent = parent
        self.child = None

    def __call__(self, identify, bp=0, auto_commit = True):
        s = self.env.get(identify)
        if not s:
            s = self._search_identify(identify)
            if not s:
                class s(Token):
                    pass
                if auto_commit:
                    s.__name__ = 'symbol-{}'.format(identify)
                    s.id = identify
                    s.lbp = bp
                    self.env[identify] = s
                else:
                    s = None
            else:
                s.lbp = max(s.lbp, bp)
        else:
            s.lbp = max(s.lbp, bp)
        return s

    def _search_identify(self, identify):
        if not self.parent:
            return None
        else:
            parent = self.parent
            value = parent.env.get(identify)
            if value:
                return value
            else:
                return parent._search_identify(identify)


    def fork_env(self):
        _new_env = type(self)(self)
        self.child_env = _new_env
        return _new_env