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 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)
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：
