readability.py

# -*- coding: utf-8 -*-

# Adadpted from here: http://acdx.net/calculating-the-flesch-kincaid-level-in-python/
# See here for details: http://en.wikipedia.org/wiki/Flesch%E2%80%93Kincaid_readability_test

from __future__ import division
import re


def mean(seq):
    return sum(seq) / len(seq)


def syllables(word):
    if len(word) <= 3:
        return 1

    word = re.sub(r"(es|ed|(?<!l)e)$", "", word)
    return len(re.findall(r"[aeiouy]+", word))


def normalize(text):
    terminators = ".!?:;"
    term = re.escape(terminators)
    text = re.sub(r"[^%s\sA-Za-z]+" % term, "", text)
    text = re.sub(r"\s*([%s]+\s*)+" % term, ". ", text)
    return re.sub(r"\s+", " ", text)


def text_stats(text, wc):
    text = normalize(text)
    stcs = [s.split(" ") for s in text.split(". ")]
    stcs = [s for s in stcs if len(s) >= 2]

    if wc:
        words = wc
    else:
        words = sum(len(s) for s in stcs)

    sbls = sum(syllables(w) for s in stcs for w in s)

    return len(stcs), words, sbls


def flesch_index(stats):
    stcs, words, sbls = stats
    if stcs == 0 or words == 0:
        return 0
    return 206.835 - 1.015 * (words / stcs) - 84.6 * (sbls / words)


def flesch_kincaid_level(stats):
    stcs, words, sbls = stats
    if stcs == 0 or words == 0:
        return 0
    return 0.39 * (words / stcs) + 11.8 * (sbls / words) - 15.59