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count_frequency_characters.py
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count_frequency_characters.py
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# Crypto Analysis: Frequency Analysis
#
# To analyze encrypted messages, to find out information about the possible
# algorithm or even language of the clear text message, one could perform
# frequency analysis. This process could be described as simply counting
# the number of times a certain symbol occurs in the given text.
# For example:
# For the text "test" the frequency of 'e' is 1, 's' is 1 and 't' is 2.
#
# The input to the function will be an encrypted body of text that only contains
# the lowercase letters a-z.
# As output you should return a list of the normalized frequency
# for each of the letters a-z.
# The normalized frequency is simply the number of occurrences, i,
# divided by the total number of characters in the message, n.
letter=('a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z')
def freq_analysis(message):
freq_list=[]
n=len(message)
for e in letter:
count=0.0
for f in message:
if f==e:
count = count+1
freq_list.append(count/n)
return freq_list
#Tests
print freq_analysis("abcd")
#>>> [0.25, 0.25, 0.25, 0.25, 0.0, ..., 0.0]
print freq_analysis("adca")
#>>> [0.5, 0.0, 0.25, 0.25, 0.0, ..., 0.0]
print freq_analysis('bewarethebunnies')
#>>> [0.0625, 0.125, 0.0, 0.0, ..., 0.0]