readability.py

"""
https://cs50.harvard.edu/x/2023/psets/6/readability/
"""

def main():

    sentence = input("Text: ")

    # Number of letters, words and sentences in the string.
    letters = count_letters(sentence)
    words = count_words(sentence)
    sentences = count_sentences(sentence)

    # Average number of letters and stentences per 100 words in text.
    avg_letters = (100 / float(words)) * float(letters)
    avg_sentences = (100 / float(words)) * float(sentences)

    # Coleman-Liau index.
    index = calculate_index(avg_letters, avg_sentences)

    if index < 1:
        print("Before Grade 1")
    elif index >= 16:
        print("Grade 16+")
    else:
        print(f"Grade {index}")


def count_letters(sentence):
    """Counts and returns the number of letters in a string."""

    letters = 0

    for character in sentence:
        if character.isalpha():
            letters += 1

    return letters


def count_words(sentence):
    """Counts and returns the number of words in a string."""

    return len(sentence.split())


def count_sentences(sentence):
    """Counts and returns the number of sentences in a string."""

    sentences = 0

    for character in sentence:
        if character in [".", "!", "?"]:
            sentences += 1

    return sentences


def calculate_index(avg_letters, avg_sentences):
    """Calculates the approximate grade level needed to comprehend some text according to the Coleman-Liau formula. Returns the result of the formula."""

    return round(0.0588 * avg_letters - 0.296 * avg_sentences - 15.8)


if __name__ == "__main__":
    main()