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69 lines
2.2 KiB
Python
69 lines
2.2 KiB
Python
# Frequency Finder
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# frequency taken from http://en.wikipedia.org/wiki/Letter_frequency
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englishLetterFreq = {'E': 12.70, 'T': 9.06, 'A': 8.17, 'O': 7.51, 'I': 6.97,
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'N': 6.75, 'S': 6.33, 'H': 6.09, 'R': 5.99, 'D': 4.25,
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'L': 4.03, 'C': 2.78, 'U': 2.76, 'M': 2.41, 'W': 2.36,
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'F': 2.23, 'G': 2.02, 'Y': 1.97, 'P': 1.93, 'B': 1.29,
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'V': 0.98, 'K': 0.77, 'J': 0.15, 'X': 0.15, 'Q': 0.10,
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'Z': 0.07}
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ETAOIN = 'ETAOINSHRDLCUMWFGYPBVKJXQZ'
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LETTERS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
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def getLetterCount(message):
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letterCount = {'A': 0, 'B': 0, 'C': 0, 'D': 0, 'E': 0, 'F': 0, 'G': 0, 'H': 0,
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'I': 0, 'J': 0, 'K': 0, 'L': 0, 'M': 0, 'N': 0, 'O': 0, 'P': 0,
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'Q': 0, 'R': 0, 'S': 0, 'T': 0, 'U': 0, 'V': 0, 'W': 0, 'X': 0,
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'Y': 0, 'Z': 0}
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for letter in message.upper():
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if letter in LETTERS:
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letterCount[letter] += 1
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return letterCount
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def getItemAtIndexZero(x):
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return x[0]
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def getFrequencyOrder(message):
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letterToFreq = getLetterCount(message)
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freqToLetter = {}
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for letter in LETTERS:
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if letterToFreq[letter] not in freqToLetter:
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freqToLetter[letterToFreq[letter]] = [letter]
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else:
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freqToLetter[letterToFreq[letter]].append(letter)
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for freq in freqToLetter:
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freqToLetter[freq].sort(key = ETAOIN.find, reverse = True)
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freqToLetter[freq] = ''.join(freqToLetter[freq])
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freqPairs = list(freqToLetter.items())
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freqPairs.sort(key = getItemAtIndexZero, reverse = True)
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freqOrder = []
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for freqPair in freqPairs:
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freqOrder.append(freqPair[1])
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return ''.join(freqOrder)
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def englishFreqMatchScore(message):
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'''
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>>> englishFreqMatchScore('Hello World')
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1
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'''
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freqOrder = getFrequencyOrder(message)
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matchScore = 0
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for commonLetter in ETAOIN[:6]:
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if commonLetter in freqOrder[:6]:
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matchScore += 1
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for uncommonLetter in ETAOIN[-6:]:
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if uncommonLetter in freqOrder[-6:]:
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matchScore += 1
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return matchScore
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if __name__ == '__main__':
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import doctest
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doctest.testmod()
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