模式特点：给定一个语言，定义它的文法的一种表示，并定义一个解释器，这个解释器使用该表示来解释语言中的句子。
我们来看一下下面这样的程序结构：
class context: def __init__(self): self.input= self.output=class abstractexpression: def interpret(self,context): passclass expression(abstractexpression): def interpret(self,context): print terminal interpretclass nonterminalexpression(abstractexpression): def interpret(self,context): print nonterminal interpretif __name__ == __main__: context= c = [] c = c + [expression()] c = c + [nonterminalexpression()] c = c + [expression()] c = c + [expression()] for a in c: a.interpret(context)
那么它所体现出的类图是这样的：
再来看一个例子：
#encoding=utf-8 # #by panda #解释器模式 def printinfo(info): print unicode(info, 'utf-8').encode('gbk'), #上下文类：演奏内容 class playcontext(): text = none playtext = none #抽象表达式类 class expression(): def interpret(self, context): if len(context.playtext) == 0: return else: playkey = context.playtext[0:1] context.playtext = context.playtext[2:] tmp = context.playtext.index(' ') #找出第一个空格出现的位置 playvalue = context.playtext[0:tmp] context.playtext = context.playtext[tmp+1:] self.excute(playkey,playvalue) def excute(self,playkey,playvalue): pass #音高 class pitch(expression): pitch = none def excute(self, key, value): value = int(value) if value == 1: self.pitch = '低音' elif value == 2: self.pitch = '中音' elif value == 3: self.pitch = '高音' printinfo(self.pitch) #音符 class note(expression): notes = { 'c':1, 'd':2, 'e':3, 'f':4, 'g':5, 'a':6, 'b':7, } note = none def excute(self, key, value): self.note = self.notes[key] printinfo('%d' % self.note) def clientui(): context = playcontext() context.playtext = o 2 e 0.5 g 0.5 a 3 e 0.5 g 0.5 d 3 e 0.5 g 0.5 a 0.5 o 3 c 1 o 2 a 0.5 g 1 c 0.5 e 0.5 d 3 expression = none; while(len(context.playtext) > 0): str = context.playtext[0:1]; if(str == 'o'): expression = pitch() elif(str == 'c' or str == 'd' or str == 'e' or str == 'f' or str == 'g' or str == 'a' or str == 'b' or str == 'p'): expression = note() expression.interpret(context) return if __name__ == '__main__': clientui();
类图：