wordfreq 1.5.1

Author: Rob Speer

## Installation

wordfreq requires Python 3 and depends on a few other Python modules (msgpack-python, langcodes, and ftfy). You can install it and its dependencies in the usual way, either by getting it from pip:

pip3 install wordfreq

or by getting the repository and running its setup.py:

python3 setup.py install

## Additional CJK installation

Chinese, Japanese, and Korean have additional external dependencies so that they can be tokenized correctly. Here we’ll explain how to set them up, in increasing order of difficulty.

### Chinese

To be able to look up word frequencies in Chinese, you need Jieba, a pure-Python Chinese tokenizer:

pip3 install jieba

### Japanese

We use MeCab, by Taku Kudo, to tokenize Japanese. To use this in wordfreq, three things need to be installed:

• The MeCab development library (called libmecab-dev on Ubuntu)

• The UTF-8 version of the ipadic Japanese dictionary (called mecab-ipadic-utf8 on Ubuntu)

• The mecab-python3 Python interface

To install these three things on Ubuntu, you can run:

`sh sudo apt-get install libmecab-dev mecab-ipadic-utf8 pip3 install mecab-python3 `

If you choose to install ipadic from somewhere else or from its source code, be sure it’s configured to use UTF-8. By default it will use EUC-JP, which will give you nonsense results.

### Korean

Korean also uses MeCab, with a Korean dictionary package by Yongwoon Lee and Yungho Yu. This dictionary is not available as an Ubuntu package.

Here’s a process you can use to install the Korean dictionary and the other MeCab dependencies:

`sh sudo apt-get install libmecab-dev mecab-utils pip3 install mecab-python3 wget https://bitbucket.org/eunjeon/mecab-ko-dic/downloads/mecab-ko-dic-2.0.1-20150920.tar.gz tar xvf mecab-ko-dic-2.0.1-20150920.tar.gz cd mecab-ko-dic-2.0.1-20150920 ./autogen.sh make sudo make install `

If wordfreq cannot find the Japanese or Korean data for MeCab when asked to tokenize those languages, it will raise an error and show you the list of paths it searched.

Sorry that this is difficult. We tried to just package the data files we need with wordfreq, like we do for Chinese, but PyPI would reject the package for being too large.

## Usage

wordfreq provides access to estimates of the frequency with which a word is used, in 27 languages (see Supported languages below).

It provides three kinds of pre-built wordlists:

• ‘combined’ lists, containing words that appear at least once per million words, averaged across all data sources.

• ‘twitter’ lists, containing words that appear at least once per million words on Twitter alone.

• ‘large’ lists, containing words that appear at least once per 100 million words, averaged across all data sources.

The most straightforward function is:

word_frequency(word, lang, wordlist=’combined’, minimum=0.0)

This function looks up a word’s frequency in the given language, returning its frequency as a decimal between 0 and 1. In these examples, we’ll multiply the frequencies by a million (1e6) to get more readable numbers:

>>> from wordfreq import word_frequency
>>> word_frequency('cafe', 'en') * 1e6
12.88249551693135

>>> word_frequency('café', 'en') * 1e6
3.3884415613920273

>>> word_frequency('cafe', 'fr') * 1e6
2.6302679918953817

>>> word_frequency('café', 'fr') * 1e6
87.09635899560814

zipf_frequency is a variation on word_frequency that aims to return the word frequency on a human-friendly logarithmic scale. The Zipf scale was proposed by Marc Brysbaert, who created the SUBTLEX lists. The Zipf frequency of a word is the base-10 logarithm of the number of times it appears per billion words. A word with Zipf value 6 appears once per thousand words, for example, and a word with Zipf value 3 appears once per million words.

Reasonable Zipf values are between 0 and 8, but because of the cutoffs described above, the minimum Zipf value appearing in these lists is 1.0 for the ‘large’ wordlists and 3.0 for all others. We use 0 as the default Zipf value for words that do not appear in the given wordlist, although it should mean one occurrence per billion words.

>>> from wordfreq import zipf_frequency
>>> zipf_frequency('the', 'en')
7.67

>>> zipf_frequency('word', 'en')
5.39

>>> zipf_frequency('frequency', 'en')
4.19

>>> zipf_frequency('zipf', 'en')
0.0

>>> zipf_frequency('zipf', 'en', wordlist='large')
1.65

The parameters to word_frequency and zipf_frequency are:

• word: a Unicode string containing the word to look up. Ideally the word is a single token according to our tokenizer, but if not, there is still hope – see Tokenization below.

• lang: the BCP 47 or ISO 639 code of the language to use, such as ‘en’.

• wordlist: which set of word frequencies to use. Current options are ‘combined’, ‘twitter’, and ‘large’.

• minimum: If the word is not in the list or has a frequency lower than minimum, return minimum instead. You may want to set this to the minimum value contained in the wordlist, to avoid a discontinuity where the wordlist ends.

Other functions:

tokenize(text, lang) splits text in the given language into words, in the same way that the words in wordfreq’s data were counted in the first place. See Tokenization.

top_n_list(lang, n, wordlist=’combined’) returns the most common n words in the list, in descending frequency order.

>>> from wordfreq import top_n_list
>>> top_n_list('en', 10)
['the', 'i', 'to', 'a', 'and', 'of', 'you', 'in', 'that', 'is']

>>> top_n_list('es', 10)
['de', 'que', 'la', 'y', 'a', 'en', 'el', 'no', 'los', 'es']

iter_wordlist(lang, wordlist=’combined’) iterates through all the words in a wordlist, in descending frequency order.

get_frequency_dict(lang, wordlist=’combined’) returns all the frequencies in a wordlist as a dictionary, for cases where you’ll want to look up a lot of words and don’t need the wrapper that word_frequency provides.

supported_languages(wordlist=’combined’) returns a dictionary whose keys are language codes, and whose values are the data file that will be loaded to provide the requested wordlist in each language.

random_words(lang=’en’, wordlist=’combined’, nwords=5, bits_per_word=12) returns a selection of random words, separated by spaces. bits_per_word=n will select each random word from 2^n words.

If you happen to want an easy way to get [a memorable, xkcd-style password][xkcd936] with 60 bits of entropy, this function will almost do the job. In this case, you should actually run the similar function random_ascii_words, limiting the selection to words that can be typed in ASCII.

[xkcd936]: https://xkcd.com/936/

## Sources and supported languages

We compiled word frequencies from seven different sources, providing us examples of word usage on different topics at different levels of formality. The sources (and the abbreviations we’ll use for them) are:

• LeedsIC: The Leeds Internet Corpus

• SUBTLEX: The SUBTLEX word frequency lists

• OpenSub: Data derived from OpenSubtitles but not from SUBTLEX

• Twitter: Messages sampled from Twitter’s public stream

• Wpedia: The full text of Wikipedia in 2015

• Reddit: The corpus of Reddit comments through May 2015

• CCrawl: Text extracted from the Common Crawl and language-detected with cld2

• Other: We get additional English frequencies from Google Books Syntactic Ngrams 2013, and Chinese frequencies from the frequency dictionary that comes with the Jieba tokenizer.

The following 27 languages are supported, with reasonable tokenization and at least 3 different sources of word frequencies:

Language Code Sources Large? SUBTLEX OpenSub LeedsIC Twitter Wpedia CCrawl Reddit Other ───────────────────────────────────┼────────────────────────────────────────────────────────────── Arabic ar 5 Yes │ - Yes Yes Yes Yes Yes - - Bulgarian bg 3 - │ - Yes - - Yes Yes - - Catalan ca 3 - │ - Yes - Yes Yes - - - Danish da 3 - │ - Yes - - Yes Yes - - German de 5 Yes │ Yes - Yes Yes Yes Yes - - Greek el 4 - │ - Yes Yes - Yes Yes - - English en 7 Yes │ Yes Yes Yes Yes Yes - Yes Google Books Spanish es 6 Yes │ - Yes Yes Yes Yes Yes Yes - Finnish fi 3 - │ - Yes - - Yes Yes - - French fr 5 Yes │ - Yes Yes Yes Yes Yes - - Hebrew he 4 - │ - Yes - Yes Yes Yes - - Hindi hi 3 - │ - - - Yes Yes Yes - - Hungarian hu 3 - │ - Yes - - Yes Yes - - Indonesian id 4 - │ - Yes - Yes Yes Yes - - Italian it 5 Yes │ - Yes Yes Yes Yes Yes - - Japanese ja 4 - │ - - Yes Yes Yes Yes - - Korean ko 3 - │ - - - Yes Yes Yes - - Malay ms 4 - │ - Yes - Yes Yes Yes - - Norwegian nb[1] 3 - │ - Yes - - Yes Yes - - Dutch nl 5 Yes │ Yes Yes - Yes Yes Yes - - Polish pl 4 - │ - Yes - Yes Yes Yes - - Portuguese pt 5 Yes │ - Yes Yes Yes Yes Yes - - Romanian ro 3 - │ - Yes - - Yes Yes - - Russian ru 5 Yes │ - Yes Yes Yes Yes Yes - - Swedish sv 4 - │ - Yes - Yes Yes Yes - - Turkish tr 4 - │ - Yes - Yes Yes Yes - - Chinese zh[2] 5 - │ Yes - Yes - Yes Yes - Jieba

[1] The Norwegian text we have is specifically written in Norwegian Bokmål, so we give it the language code ‘nb’. We would use ‘nn’ for Nynorsk, but there isn’t enough data to include it in wordfreq.

[2] This data represents text written in both Simplified and Traditional Chinese. (SUBTLEX is mostly Simplified, while Wikipedia is mostly Traditional.) The characters are mapped to one another so they can use the same word frequency list.

Some languages provide ‘large’ wordlists, including words with a Zipf frequency between 1.0 and 3.0. These are available in 9 languages that are covered by enough data sources.

## Tokenization

wordfreq uses the Python package regex, which is a more advanced implementation of regular expressions than the standard library, to separate text into tokens that can be counted consistently. regex produces tokens that follow the recommendations in [Unicode Annex #29, Text Segmentation][uax29], including the optional rule that splits words between apostrophes and vowels.

There are language-specific exceptions:

• In Arabic and Hebrew, it additionally normalizes ligatures and removes combining marks.

• In Japanese and Korean, instead of using the regex library, it uses the external library mecab-python3. This is an optional dependency of wordfreq, and compiling it requires the libmecab-dev system package to be installed.

• In Chinese, it uses the external Python library jieba, another optional dependency.

[uax29]: http://unicode.org/reports/tr29/

When wordfreq’s frequency lists are built in the first place, the words are tokenized according to this function.

Because tokenization in the real world is far from consistent, wordfreq will also try to deal gracefully when you query it with texts that actually break into multiple tokens:

>>> zipf_frequency('New York', 'en')
5.07
>>> zipf_frequency('北京地铁', 'zh')  # "Beijing Subway"
3.58

The word frequencies are combined with the half-harmonic-mean function in order to provide an estimate of what their combined frequency would be. In Chinese, where the word breaks must be inferred from the frequency of the resulting words, there is also a penalty to the word frequency for each word break that must be inferred.

This method of combining word frequencies implicitly assumes that you’re asking about words that frequently appear together. It’s not multiplying the frequencies, because that would assume they are statistically unrelated. So if you give it an uncommon combination of tokens, it will hugely over-estimate their frequency:

>>> zipf_frequency('owl-flavored', 'en')
3.19

## License

wordfreq is freely redistributable under the MIT license (see MIT-LICENSE.txt), and it includes data files that may be redistributed under a Creative Commons Attribution-ShareAlike 4.0 license (https://creativecommons.org/licenses/by-sa/4.0/).

wordfreq contains data extracted from Google Books Ngrams (http://books.google.com/ngrams) and Google Books Syntactic Ngrams (http://commondatastorage.googleapis.com/books/syntactic-ngrams/index.html). The terms of use of this data are:

Ngram Viewer graphs and data may be freely used for any purpose, although acknowledgement of Google Books Ngram Viewer as the source, and inclusion of a link to http://books.google.com/ngrams, would be appreciated.

wordfreq also contains data derived from the following Creative Commons-licensed sources:

• The Leeds Internet Corpus, from the University of Leeds Centre for Translation Studies (http://corpus.leeds.ac.uk/list.html)

• The OpenSubtitles Frequency Word Lists, compiled by Hermit Dave (https://invokeit.wordpress.com/frequency-word-lists/)

• Wikipedia, the free encyclopedia (http://www.wikipedia.org)

It contains data from various SUBTLEX word lists: SUBTLEX-US, SUBTLEX-UK, SUBTLEX-CH, SUBTLEX-DE, and SUBTLEX-NL, created by Marc Brysbaert et al. (see citations below) and available at http://crr.ugent.be/programs-data/subtitle-frequencies.

I (Rob Speer) have obtained permission by e-mail from Marc Brysbaert to distribute these wordlists in wordfreq, to be used for any purpose, not just for academic use, under these conditions:

• Wordfreq and code derived from it must credit the SUBTLEX authors.

• It must remain clear that SUBTLEX is freely available data.

These terms are similar to the Creative Commons Attribution-ShareAlike license.

Some additional data was collected by a custom application that watches the streaming Twitter API, in accordance with Twitter’s Developer Agreement & Policy. This software gives statistics about words that are commonly used on Twitter; it does not display or republish any Twitter content.

## Citations to work that wordfreq is built on

• Brysbaert, M. & New, B. (2009). Moving beyond Kucera and Francis: A Critical Evaluation of Current Word Frequency Norms and the Introduction of a New and Improved Word Frequency Measure for American English. Behavior Research Methods, 41 (4), 977-990. http://sites.google.com/site/borisnew/pub/BrysbaertNew2009.pdf

• Brysbaert, M., Buchmeier, M., Conrad, M., Jacobs, A. M., Bölte, J., & Böhl, A. (2015). The word frequency effect. Experimental Psychology. http://econtent.hogrefe.com/doi/abs/10.1027/1618-3169/a000123?journalCode=zea

• Brysbaert, M., Buchmeier, M., Conrad, M., Jacobs, A.M., Bölte, J., & Böhl, A. (2011). The word frequency effect: A review of recent developments and implications for the choice of frequency estimates in German. Experimental Psychology, 58, 412-424.

• Cai, Q., & Brysbaert, M. (2010). SUBTLEX-CH: Chinese word and character frequencies based on film subtitles. PLoS One, 5(6), e10729. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0010729

• Dave, H. (2011). Frequency word lists. https://invokeit.wordpress.com/frequency-word-lists/

• Davis, M. (2012). Unicode text segmentation. Unicode Standard Annex, 29. http://unicode.org/reports/tr29/

• Keuleers, E., Brysbaert, M. & New, B. (2010). SUBTLEX-NL: A new frequency measure for Dutch words based on film subtitles. Behavior Research Methods, 42(3), 643-650. http://crr.ugent.be/papers/SUBTLEX-NL_BRM.pdf

• Kudo, T. (2005). Mecab: Yet another part-of-speech and morphological analyzer. http://mecab.sourceforge.net/

• van Heuven, W. J., Mandera, P., Keuleers, E., & Brysbaert, M. (2014). SUBTLEX-UK: A new and improved word frequency database for British English. The Quarterly Journal of Experimental Psychology, 67(6), 1176-1190. http://www.tandfonline.com/doi/pdf/10.1080/17470218.2013.850521