[GO] CheckIO (Python)> The Most Wanted Letter I tried> Searching for the most frequent alphabets> Using Counter in collections, using filter () and sorted (), method by keying max (), string.ascii_lowercase

I was curious about the site called CheckIO and tried it.

I tried the following tasks.

https://py.checkio.org/mission/most-wanted-letter/solve/

Task

You are given a text, which contains different english letters and punctuation symbols. You should find the most frequent letter in the text. The letter returned must be in lower case. While checking for the most wanted letter, casing does not matter, so for the purpose of your search, "A" == "a". Make sure you do not count punctuation symbols, digits and whitespaces, only letters. If you have two or more letters with the same frequency, then return the letter which comes first in the latin alphabet. For example -- "one" contains "o", "n", "e" only once for each, thus we choose "e". Input: A text for analysis as a string. Output: The most frequent letter in lower case as a string. Precondition: A text contains only ASCII symbols. 0 < len(text) ≤ 10^5

Implementation

from collections import Counter

def checkio(text):
    print(text)
    counter = Counter(text.lower())
    firstalph, itscount = 'z', 0
    for word, cnt in counter.most_common():
        if word < 'a':
            continue
        if (itscount <= cnt) and (firstalph >= word):
            firstalph = word
            itscount = cnt
            #print('found',firstalph)
        #print(word, cnt)
    return firstalph

if __name__ == '__main__':
    #These "asserts" using only for self-checking and not necessary for auto-testing
    assert checkio("Hello World!") == "l", "Hello test"
    assert checkio("How do you do?") == "o", "O is most wanted"
    assert checkio("One") == "e", "All letter only once."
    assert checkio("Oops!") == "o", "Don't forget about lower case."
    assert checkio("AAaooo!!!!") == "a", "Only letters."
    assert checkio("abe") == "a", "The First."
    assert checkio("zzzz...sleepy") == "z", "The First."
    print("Start the long test")
    assert checkio("a" * 9000 + "b" * 1000) == "a", "Long."
    print("The local tests are done.")

There was no problem with all assertions. However, text (example: "*** !!!") composed of character strings other than a..z is not supported.

run

Hello World!
How do you do?
One
Oops!
AAaooo!!!!
abe
zzzz...sleepy
Start the long test
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
The local tests are done.

Related Links

Reference: Counter is useful for counting words in Python

Link: http://docs.python.jp/3/library/collections.html

v0.2> used version of filter () and sorted ()

It could also be implemented using filter () and sorted (). The readability of lines using filter () is not good.

from collections import Counter

def checkio(text):
    print(text)
    counter = Counter(text.lower())
    alist = list(filter(lambda x:'a' <= x[0] <= 'z', counter.most_common()))
    alist = sorted(alist, key=lambda x:(-x[1],x[0]))
    firstalph = alist[0][0]
    return firstalph

if __name__ == '__main__':
    #These "asserts" using only for self-checking and not necessary for auto-testing
    assert checkio("Hello World!") == "l", "Hello test"
    assert checkio("How do you do?") == "o", "O is most wanted"
    assert checkio("One") == "e", "All letter only once."
    assert checkio("Oops!") == "o", "Don't forget about lower case."
    assert checkio("AAaooo!!!!") == "a", "Only letters."
    assert checkio("abe") == "a", "The First."
    assert checkio("zzzz...sleepy") == "z", "The First."
    print("Start the long test")
    assert checkio("a" * 9000 + "b" * 1000) == "a", "Long."
    print("The local tests are done.")

filter: https://docs.python.jp/3/library/functions.html#filter sorted: https://docs.python.jp/3/library/functions.html#sorted

Matters taught

(Addition 2017/07/26)

@ shiracamus's Comment taught me how to specify the key of max ().

Thank you for the information.