Exactly two years ago, I was playing with NLTK for a readability index. Now with this readability (GitHub), which really makes this task much easier, here is an example out on this blog’s About page:


readability grades:
    Kincaid:                     4.74
    ARI:                         6.01
    Coleman-Liau:                8.87
    FleschReadingEase:          80.75
    GunningFogIndex:             8.2
    LIX:                        33.27
    SMOGIndex:                   8.6
    RIX:                         2.46
sentence info:
    characters_per_word:         4.65
    syll_per_word:               1.36
    words_per_sentence:         11.07
    sentences_per_paragraph:         2.56
    characters:               2367
    syllables:                 691
    words:                     509
    sentences:                  46
    paragraphs:                 18
    long_words:                113
    complex_words:              48
word usage:
    tobeverb:                   12
    auxverb:                    14
    conjunction:                16
    pronoun:                    68
    preposition:                50
    nominalization:             12
sentence beginnings:
    pronoun:                     6
    interrogative:               0
    article:                     0
    subordination:               1
    conjunction:                 0
    preposition:                 1

One command and you have lots of readability indexes, and it supports more than English language, also with Dutch and German languages.

readability is written by Andreas van Cranenburgh and Max Mautner, based on NLTK, under Apache License Version 2.0, currently version 0.1 (2014-04-13).