解释器模式

class Context:
    def __init__(self):
        self.input=""
        self.output=""

class AbstractExpression:
    def Interpret(self,context):
        pass

class Expression(AbstractExpression):
    def Interpret(self,context):
        print ("terminal interpret")

class NonterminalExpression(AbstractExpression):
    def Interpret(self,context):
        print ("Nonterminal interpret")

if __name__ == "__main__":
    context= ""
    c = []
    c = c + [Expression()]
    c = c + [NonterminalExpression()]
    c = c + [Expression()]
    c = c + [Expression()]
    for a in c:
        a.Interpret(context)