Development - Advanced, exercise 19

Text

The Coleman–Liau index (CLI) is a readability test for English texts, designed to gauge the understandability of a text by representing the US grade level needed to comprehend such text. The formula for calculating the CLI is the following one:

CLI = 0.0588 * L – 0.296 * S – 15.8

where, considering a given text, L is the average number of alphabetic characters and digits (no punctuation and spaces are considered here) per 100 words and S is the average number of sentences per 100 words.

Write an algorithm in Python – def cli(text) – which returns the CLI of the text specified in input.

Solution

# Test case for the function
def test_cli(text, expected):
    result = cli(text)
    if round(expected, 3) == round(result, 3):
        return True
    else:
        return False


# Code of the function
def cli(text):
    n_words = len(text.split(" "))

    n_chars = 0
    n_sentences = 0
    for c in text.lower():
        if c in "qwertyuiopasdfghjklzxcvbnm1234567890":
            n_chars = n_chars + 1
        if c in ".!?;:":
            n_sentences = n_sentences + 1
    
    l = (n_chars / n_words) * 100
    s = (n_sentences / n_words) * 100
    
    return 0.0588 * l - 0.296 * s - 15.8


# Tests
print(test_cli("Test.", 0.0588 * (4 / 1) * 100 - 0.296 * (1 / 1) * 100 - 15.8))
print(test_cli("After a while, finding that nothing more happened, she decided on going into the garden at once; but, alas for poor Alice! when she got to the door, she found she had forgotten the little golden key, and when she went back to the table for it, she found she could not possibly reach it: she could see it quite plainly through the glass, and she tried her best to climb up one of the legs of the table, but it was too slippery; and when she had tired herself out with trying, the poor little thing sat down and cried.", 0.0588 * (402 / 101) * 100 - 0.296 * (5 / 101) * 100 - 15.8))

Additional material

The runnable Python file is available online.