1 """TemplateMethodPattern in DesignPatterns Example
   2 """
   3 
   4 import unittest, sys
   5 from cStringIO import StringIO
   6 
   7 class Singer:
   8     """children should implement..."""
   9     def __init__(self,aStream):
  10         self.stream=aStream
  11     def sing(self):
  12         self.beforeSing()
  13         self.singTheSong()
  14         self.endingWords()
  15     def beforeSing(self):
  16         raise NotImplementedError    
  17         
  18 class PoPSinger(Singer):
  19     def beforeSing(self):
  20         self.askAudience()
  21     def singTheSong(self):
  22         raise NotImplementedError
  23     
  24 class FolkSongSinger(Singer):
  25     def beforeSing(self):
  26         self.gatherMoney()
  27     def singTheSong(self):
  28         raise NotImplementedError
  29         
  30 class HeavyMetalSinger(PoPSinger):
  31     def askAudience(self):
  32         print >>self.stream,"Are you ready?"
  33     def singTheSong(self):
  34         print >>self.stream,"blah blah blah metal and blah..."
  35         print >>self.stream,"(He's jumping into the audience)"
  36         print >>self.stream,"(comes back to the stage crawling)"
  37     def endingWords(self):
  38         print >>self.stream,"Thank you, guys!"        
  39 
  40 class OperaSinger(PoPSinger):
  41     def askAudience(self):
  42         print >>self.stream,"Ladies, and gentlemen..."
  43     def singTheSong(self):
  44         print >>self.stream,"blah blah very romantic blah blah..."
  45         print >>self.stream,"(He's waving his hands very gracefully)"
  46     def endingWords(self):
  47         print >>self.stream,"Thank you very much."
  48         
  49 class TestAll(unittest.TestCase):
  50     def testAll(self):
  51         testStream=StringIO()
  52         heavyMetalSinger=HeavyMetalSinger(testStream)
  53         heavyMetalSinger.sing()
  54         expected="""Are you ready?
  55 blah blah blah metal and blah...
  56 (He's jumping into the audience)
  57 (comes back to the stage crawling)
  58 Thank you, guys!
  59 """
  60         self.assertEquals(expected,testStream.getvalue())
  61         testStream=StringIO()
  62         operaSinger=OperaSinger(testStream)
  63         operaSinger.sing()
  64         expected="""Ladies, and gentlemen...
  65 blah blah very romantic blah blah...
  66 (He's waving his hands very gracefully)
  67 Thank you very much.
  68 """
  69         self.assertEquals(expected,testStream.getvalue())
  70 
  71 if __name__=='__main__':
  72     unittest.main()