306 http://inventwithpython.com/hacking

Email questions to the author: [email protected]

45. 
    

    third, put each list of letters in reverse "ETAOIN" order, and then

    
    


46. 
    

    convert it to a string

    
    


47. for freq in freqToLetter:


48. freqToLetter[freq].sort(key=ETAOIN.find, reverse=True)


49. freqToLetter[freq] = ''.join(freqToLetter[freq])


50. 
    


51. 
    

    fourth, convert the freqToLetter dictionary to a list of tuple

    
    


52. 
    

    pairs (key, value), then sort them

    
    


53. freqPairs = list(freqToLetter.items())


54. freqPairs.sort(key=getItemAtIndexZero, reverse=True)


55. 
    


56. 
    

    fifth, now that the letters are ordered by frequency, extract all

    
    


57. 
    

    the letters for the final string

    
    


58. freqOrder = []


59. for freqPair in freqPairs:


60. freqOrder.append(freqPair[1])


61. 
    


62. return ''.join(freqOrder)


63. 
    


64. 
    


65. def englishFreqMatchScore(message):


66. 
    

    Return the number of matches that the string in the message

    
    


67. 
    

    parameter has when its letter frequency is compared to English

    
    


68. 
    

    letter frequency. A "match" is how many of its six most frequent

    
    


69. 
    

    and six least frequent letters is among the six most frequent and

    
    


70. 
    

    six least frequent letters for English.

    
    


71. freqOrder = getFrequencyOrder(message)


72. 
    


73. matchScore = 0


74. 
    

    Find how many matches for the six most common letters there are.

    
    


75. for commonLetter in ETAOIN[:6]:


76. if commonLetter in freqOrder[:6]:


77. matchScore += 1


78. 
    

    Find how many matches for the six least common letters there are.

    
    


79. for uncommonLetter in ETAOIN[-6:]:


80. if uncommonLetter in freqOrder[-6:]:


81. matchScore += 1


82. 
    


83. return matchScore

How the Program Works..........................................................................................................................................

freqAnalysis.py

1. 
   

   Frequency Finder

   
   


2. 
   

   http://inventwithpython.com/hacking (BSD Licensed)

   
   


3.