Function flesch_reading_ease

pattern/metrics.py:302–330

Returns the readability of the string as a value between 0.0-1.0: 0.30-0.50 (difficult) => 0.60-0.70 (standard) => 0.90-1.00 (very easy).

(string)

# 0.0-0.3 = best understood by university graduates.

def flesch_reading_ease(string):
    """ Returns the readability of the string as a value between 0.0-1.0:
        0.30-0.50 (difficult) => 0.60-0.70 (standard) => 0.90-1.00 (very easy).
    """
    def count_syllables(word, vowels="aeiouy"):
        n = 0
        p = False # True if the previous character was a vowel.
        for ch in word.endswith("e") and word[:-1] or word:
            v = ch in vowels
            n += int(v and not p)
            p = v
        return n
    if len(string) <  3:
        return 1.0
    string = string.strip()
    string = string.strip("\"&#x27;().")
    string = string.lower()
    string = string.replace("!", ".")
    string = string.replace("?", ".")
    string = string.replace(",", " ")
    y = [count_syllables(w) for w in string.split() if w != ""]
    w = len([w for w in string.split(" ") if w != ""])
    s = len([s for s in string.split(".") if len(s) > 2])
    #R = 206.835 - 1.015 * w/s - 84.6 * sum(y)/w
    # Use the Farr, Jenkins & Patterson algorithm,
    # which uses simpler syllable counting (count_syllables() is the weak point here). 
    R = 1.599 * sum(1 for v in y if v == 1) * 100 / w - 1.015*w/s - 31.517
    R = max(0.0, min(R*0.01, 1.0))
    return R

readability = flesch_reading_ease