Python - can I detect unicode string language code?

I'm faced with a situation where I'm reading a string of text and I need to detect the language code (en, de,开发者_如何学Python fr, es, etc).

Is there a simple way to do this in python?

If you need to detect language in response to a user action then you could use google ajax language API:

#!/usr/bin/env python
import json
import urllib, urllib2

def detect_language(text,
    userip=None,
    referrer="http://stackoverflow.com/q/4545977/4279",
    api_key=None):        

    query = {'q': text.encode('utf-8') if isinstance(text, unicode) else text}
    if userip: query.update(userip=userip)
    if api_key: query.update(key=api_key)

    url = 'https://ajax.googleapis.com/ajax/services/language/detect?v=1.0&%s'%(
        urllib.urlencode(query))

    request = urllib2.Request(url, None, headers=dict(Referer=referrer))
    d = json.load(urllib2.urlopen(request))

    if d['responseStatus'] != 200 or u'error' in d['responseData']:
        raise IOError(d)

    return d['responseData']['language']

print detect_language("Python - can I detect unicode string language code?")

Output

en

Google Translate API v2

Default limit 100000 characters/day (no more than 5000 at a time).

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import json
import urllib, urllib2

from operator import itemgetter

def detect_language_v2(chunks, api_key):
    """
    chunks: either string or sequence of strings

    Return list of corresponding language codes
    """
    if isinstance(chunks, basestring):
        chunks = [chunks] 

    url = 'https://www.googleapis.com/language/translate/v2'

    data = urllib.urlencode(dict(
        q=[t.encode('utf-8') if isinstance(t, unicode) else t 
           for t in chunks],
        key=api_key,
        target="en"), doseq=1)

    # the request length MUST be < 5000
    if len(data) > 5000:
        raise ValueError("request is too long, see "
            "http://code.google.com/apis/language/translate/terms.html")

    #NOTE: use POST to allow more than 2K characters
    request = urllib2.Request(url, data,
        headers={'X-HTTP-Method-Override': 'GET'})
    d = json.load(urllib2.urlopen(request))
    if u'error' in d:
        raise IOError(d)
    return map(itemgetter('detectedSourceLanguage'), d['data']['translations'])

Now you could request detecting a language explicitly:

def detect_language_v2(chunks, api_key):
    """
    chunks: either string or sequence of strings

    Return list of corresponding language codes
    """
    if isinstance(chunks, basestring):
        chunks = [chunks] 

    url = 'https://www.googleapis.com/language/translate/v2/detect'

    data = urllib.urlencode(dict(
        q=[t.encode('utf-8') if isinstance(t, unicode) else t
           for t in chunks],
        key=api_key), doseq=True)

    # the request length MUST be < 5000
    if len(data) > 5000:
        raise ValueError("request is too long, see "
            "http://code.google.com/apis/language/translate/terms.html")

    #NOTE: use POST to allow more than 2K characters
    request = urllib2.Request(url, data,
        headers={'X-HTTP-Method-Override': 'GET'})
    d = json.load(urllib2.urlopen(request))

    return [sorted(L, key=itemgetter('confidence'))[-1]['language']
            for L in d['data']['detections']]

Example:

print detect_language_v2(
    ["Python - can I detect unicode string language code?",
     u"матрёшка",
     u"打水"], api_key=open('api_key.txt').read().strip())

Output

[u'en', u'ru', u'zh-CN']

In my case I only need to determine two languages so I just check the first character:

import unicodedata

def is_greek(term):
    return 'GREEK' in unicodedata.name(term.strip()[0])


def is_hebrew(term):
    return 'HEBREW' in unicodedata.name(term.strip()[0])

Have a look at guess-language:

Attempts to determine the natural language of a selection of Unicode (utf-8) text.

But as the name says, it guesses the language. You can't expect 100% correct results.

Edit:

guess-language is unmaintained. But there is a fork (that support python3): guess_language-spirit

Look at Natural Language Toolkit and Automatic Language Identification using Python for ideas.

I would like to know if a Bayesian filter can get language right but I can't write a proof of concept right now.

A useful article here suggests that this open source named CLD is the best bet for detecting language in python.

The article shows a comparison of speed and accuracy between 3 solutions :

1. language-detection or its python port langdetect
2. Tika
3. Chromium Language Detection (CLD)

I wasted my time with langdetect now I am switching to CLD which is 16x faster than langdetect and has 98.8% accuracy

Try Universal Encoding Detector its a port of chardet module from Firefox to Python.

If you only have a limited number of possible languages, you could use a set of dictionaries (possibly only including the most common words) of each language and then check the words in your input against the dictionaries.