initial

other/frequency_finder.py

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