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):
 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)

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：