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# Frequency Finder

import string

# frequency taken from https://en.wikipedia.org/wiki/Letter_frequency

english_letter_freq = {

"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 get_letter_count(message: str) -> dict[str, int]:

letter_count = {letter: 0 for letter in string.ascii_uppercase}

for letter in message.upper():

if letter in LETTERS:

letter_count[letter] += 1

return letter_count

def get_item_at_index_zero(x: tuple) -> str:

return x[0]

def get_frequency_order(message: str) -> str:

letter_to_freq = get_letter_count(message)

freq_to_letter: dict[int, list[str]] = {

freq: [] for letter, freq in letter_to_freq.items()

}

for letter in LETTERS:

freq_to_letter[letter_to_freq[letter]].append(letter)

freq_to_letter_str: dict[int, str] = {}

for freq in freq_to_letter:

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

freq_to_letter_str[freq] = "".join(freq_to_letter[freq])

freq_pairs = list(freq_to_letter_str.items())

freq_pairs.sort(key=get_item_at_index_zero, reverse=True)

freq_order: list[str] = [freq_pair[1] for freq_pair in freq_pairs]

return "".join(freq_order)

def english_freq_match_score(message: str) -> int:

"""

>>> english_freq_match_score('Hello World')

1

"""

freq_order = get_frequency_order(message)

match_score = 0

for common_letter in ETAOIN[:6]:

if common_letter in freq_order[:6]:

match_score += 1

for uncommon_letter in ETAOIN[-6:]:

if uncommon_letter in freq_order[-6:]:

match_score += 1

return match_score

if __name__ == "__main__":

import doctest

doctest.testmod()