TheAlgorithms_Python/strings/frequency_finder.py at master · mindaugl/TheAlgorithms_Python · GitHub

Name: TheAlgorithms_Python/strings/frequency_finder.py at master · mindaugl/TheAlgorithms_Python · GitHub
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# Frequency Finder

importstring

# 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"


defget_letter_count(message: str) ->dict[str, int]:
letter_count=dict.fromkeys(string.ascii_uppercase, 0)
forletterinmessage.upper():
ifletterinLETTERS:
letter_count[letter] +=1

returnletter_count


defget_item_at_index_zero(x: tuple) ->str:
returnx[0]


defget_frequency_order(message: str) ->str:
"""
 Get the frequency order of the letters in the given string
 >>> get_frequency_order('Hello World')
 'LOWDRHEZQXJKVBPYGFMUCSNIAT'
 >>> get_frequency_order('Hello@')
 'LHOEZQXJKVBPYGFWMUCDRSNIAT'
 >>> get_frequency_order('h')
 'HZQXJKVBPYGFWMUCLDRSNIOATE'
 """
letter_to_freq=get_letter_count(message)
freq_to_letter: dict[int, list[str]] = {
freq: [] forletter, freqinletter_to_freq.items()
 }
forletterinLETTERS:
freq_to_letter[letter_to_freq[letter]].append(letter)

freq_to_letter_str: dict[int, str] = {}

forfreqinfreq_to_letter: # noqa: PLC0206
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] forfreq_pairinfreq_pairs]

return"".join(freq_order)


defenglish_freq_match_score(message: str) ->int:
"""
 >>> english_freq_match_score('Hello World')
 1
 """
freq_order=get_frequency_order(message)
match_score=0
forcommon_letterinETAOIN[:6]:
ifcommon_letterinfreq_order[:6]:
match_score+=1

foruncommon_letterinETAOIN[-6:]:
ifuncommon_letterinfreq_order[-6:]:
match_score+=1

returnmatch_score


if__name__=="__main__":
importdoctest

doctest.testmod()