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):
    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：