测试通过时间：2019-8-20
参阅：C#实现谷歌翻译API、Python之Google翻译爬虫

首先声明，没有什么不良动机，因为经常会用 translate.google.cn，就想着用 Python 模拟网页提交实现文档的批量翻译。据说有 API，可是要收费。

生成 Token

Google 为防爬虫而生成 token 的代码是 Javascript 的，且是根据网站的 TKK 值和提交的文本动态生成。
网上搜到的一段 Python 代码有点小 Bug，且缺少动态获取 TKK 的步骤。
最后还是对照 Javascript 代码自己改成 Python 了。方法很简单，先转成易懂的 Javascript，再转成 Python。Javascript 代码来自C#实现谷歌翻译API。

原始（晦涩） Javascript 代码

var b = function (a,b) {
    for (var d = 0; d < b.length - 2; d += 3) {
        var c = b.charAt(d + 2),c = "a" <= c ? c.charCodeAt(0) - 87 : Number(c),c = "+" == b.charAt(d + 1) ? a >>> c : a << c;
        a = "+" == b.charAt(d) ? a + c & 4294967295 : a ^ c
    }
    return a
}
 
var tk =  function (a,TKK) {
    for (var e = TKK.split("."),h = Number(e[0]) || 0,g = [],d = 0,f = 0; f < a.length; f++) {
        var c = a.charCodeAt(f);
        128 > c ? g[d++] = c : (2048 > c ? g[d++] = c >> 6 | 192 : (55296 == (c & 64512) && f + 1 < a.length && 56320 == (a.charCodeAt(f + 1) & 64512) ? (c = 65536 + ((c & 1023) << 10) + (a.charCodeAt(++f) & 1023),g[d++] = c >> 18 | 240,g[d++] = c >> 12 & 63 | 128) : g[d++] = c >> 12 | 224,g[d++] = c >> 6 & 63 | 128),g[d++] = c & 63 | 128)
    }
    a = h;
    for (d = 0; d < g.length; d++) a += g[d],a = b(a,"+-a^+6");
    a = b(a,"+-3^+b+-f");
    a ^= Number(e[1]) || 0;
    0 > a && (a = (a & 2147483647) + 2147483648);
    a %= 1E6;
    return a.toString() + "." + (a ^ h)
}

易懂的 Javascript 代码

function RL(a,b) {
    for (var d = 0; d < b.length - 2; d += 3) {
        var c = b.charAt(d + 2);
        c = "a" <= c ? c.charCodeAt(0) - 87 : Number(c);
        c = "+" == b.charAt(d + 1) ? a >>> c : a << c;
        a = "+" == b.charAt(d) ? a + c & 4294967295 : a ^ c;
    }
    return a
}
 
function TL(a,TKK) {
    var e = TKK.split(".");
    var h = Number(e[0]) || 0;
    var g = [];
    var d = 0;
    for (var f = 0; f < a.length; f++) {
        var c = a.charCodeAt(f);
        if (128 > c)
        {
            g[d++] = c;
        } 
        else
        {
            if (2048 > c)
            {
                g[d++] = c >> 6 | 192;
            }
            else
            {
                if (55296 == (c & 64512) && f + 1 < a.length && 56320 == (a.charCodeAt(f + 1) & 64512))
                {
                    c = 65536 + ((c & 1023) << 10) + (a.charCodeAt(++f) & 1023);
                    g[d++] = c >> 18 | 240;
                    g[d++] = c >> 12 & 63 | 128;
                }
                else
                {
                    g[d++] = c >> 12 | 224;
                    g[d++] = c >> 6 & 63 | 128;
                }
            }
            g[d++] = c & 63 | 128;
        }
    }
    a = h;
    for (var d = 0; d < g.length; d++) {
        a += g[d];
        a = b(a,"+-a^+6");
    }
    a = b(a,"+-3^+b+-f");
    a ^= Number(e[1]) || 0;
    0 > a && (a = (a & 2147483647) + 2147483648);
    a %= 1E6;
    return a.toString() + "." + (a ^ h)
}

Python 代码

def getGoogleToken(a,TKK):
    def RL(a,b):
        for d in range(0,len(b)-2,3):
            c = b[d + 2]
            c = ord(c[0]) - 87 if 'a' <= c else int(c)
            c = a >> c if '+' == b[d + 1] else a << c
            a = a + c & 4294967295 if '+' == b[d] else a ^ c
        return a

    g = []
    f = 0
    while f < len(a):
        c = ord(a[f])
        if 128 > c:
            g.append(c)
        else:
            if 2048 > c:
                g.append((c >> 6) | 192)
            else:
                if (55296 == (c & 64512)) and (f + 1 < len(a)) and (56320 == (ord(a[f+1]) & 64512)):
                    f += 1
                    c = 65536 + ((c & 1023) << 10) + (ord(a[f]) & 1023)
                    g.append((c >> 18) | 240)
                    g.append((c >> 12) & 63 | 128)
                else:
                    g.append((c >> 12) | 224)
                    g.append((c >> 6) & 63 | 128)
            g.append((c & 63) | 128)
        f += 1

    e = TKK.split('.')
    h = int(e[0]) or 0
    t = h
    for item in g:
        t += item
        t = RL(t,'+-a^+6')
    t = RL(t,'+-3^+b+-f')
    t ^= int(e[1]) or 0
    if 0 > t:
        t = (t & 2147483647) + 2147483648
    result = t % 1000000
    return str(result) + '.' + str(result ^ h)

获取 Token Key

Google 的 TKK 可以通过访问网站 https://translate.google.cn 获取，里面有段脚本里包含了“tkk:(‘xxxxxx.xxxxxx‘)”，用正则表达式截取即可。

res = requests.get('https://translate.google.cn',timeout = 3)
    res.raise_for_status()
    result = re.search(r'tkk:'(d+.d+)?'',res.text).group(1)

划分文章段落

因为常从 PDF 里复制文本翻译，这样就不能依赖换行符来划分段落了。只能判断空行，作为段落的分界。
另外 Google 返回的结果 Json 里，会以英文句点作为分隔符，每一句译文均作为数组的一项分开。所以最后得合并一下，成为一个段落。

完整代码

代码不长，全文黏贴如下。
GoogleTranslator.py：

import requests
import re
import json
import time

class GoogleTranslator ():
    _host = 'translate.google.cn'

    _headers = {
        'Host': _host,'User-Agent': 'Mozilla/5.0 (Linux; Android 6.0; Nexus 5 Build/MRA58N) AppleWebKit/537.36 (KHTML,like Gecko) Chrome/76.0.3809.100 Mobile Safari/537.36','Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8','Accept-Language': 'zh-CN,zh;q=0.8,en-US;q=0.5,en;q=0.3','Accept-Encoding': 'gzip,deflate,br','Content-Type': 'application/x-www-form-urlencoded;charset=utf-8','Referer': 'https://' + _host,'Connection': 'keep-alive','Cache-Control': 'max-age=0'
    }

    _language = {
        'afrikaans': 'af','arabic': 'ar','belarusian': 'be','bulgarian': 'bg','catalan': 'ca','czech': 'cs','welsh': 'cy','danish': 'da','german': 'de','greek': 'el','english': 'en','esperanto': 'eo','spanish': 'es','estonian': 'et','persian': 'fa','finnish': 'fi','french': 'fr','irish': 'ga','galician': 'gl','hindi': 'hi','croatian': 'hr','hungarian': 'hu','indonesian': 'id','icelandic': 'is','italian': 'it','hebrew': 'iw','japanese': 'ja','korean': 'ko','latin': 'la','lithuanian': 'lt','latvian': 'lv','macedonian': 'mk','malay': 'ms','maltese': 'mt','dutch': 'nl','norwegian': 'no','polish': 'pl','portuguese': 'pt','romanian': 'ro','russian': 'ru','slovak': 'sk','slovenian': 'sl','albanian': 'sq','serbian': 'sr','swedish': 'sv','swahili': 'sw','thai': 'th','filipino': 'tl','turkish': 'tr','ukrainian': 'uk','vietnamese': 'vi','yiddish': 'yi','chinese_simplified': 'zh-CN','chinese_traditional': 'zh-TW','auto': 'auto'
    }
    _url = 'https://' + _host + '/translate_a/single'
    _params = {
            'client': 'webapp','sl': 'en','tl': 'zh-CN','hl': 'zh-CN','dt': 'at','dt': 'bd','dt': 'ex','dt': 'ld','dt': 'md','dt': 'qca','dt': 'rw','dt': 'rm','dt': 'ss','dt': 't','otf': '1','ssel': '0','tsel': '0','kc': '1'
    }

    __cookies = None

    __googleTokenKey = '376032.257956'
    __googleTokenKeyUpdataTime = 600.0
    __googleTokenKeyRetireTime = time.time() + 600.0

    def __init__(self,src = 'en',dest = 'zh-CN',tkkUpdataTime = 600.0):
        if src not in self._language and src not in self._language.values():
            src = 'auto'
        if dest not in self._language and dest not in self._language.values():
            dest = 'auto'
        self._params['sl'] = src
        self._params['tl'] = dest
        self.googleTokenKeyUpdataTime = tkkUpdataTime
        self.__updateGoogleTokenKey()

    def __updateGoogleTokenKey(self):
        self.__googleTokenKey = self.__getGoogleTokenKey()
        self.__googleTokenKeyRetireTime = time.time() + self.__googleTokenKeyUpdataTime

    def __getGoogleTokenKey(self):
        """Get the Google TKK from https://translate.google.cn"""
        # TKK example: '435075.3634891900'
        result = ''
        try:
            res = requests.get('https://' + self._host,timeout = 3)
            res.raise_for_status()
            self.__cookies = res.cookies
            result = re.search(r'tkk:'(d+.d+)?'',res.text).group(1)
        except requests.exceptions.ReadTimeout as ex:
            print('ERROR: ' + str(ex))
            time.sleep(1)
        return result

    def __getGoogleToken(self,a,TKK):
        """Calculate Google tk from TKK """
        # https://www.cnblogs.com/chicsky/p/7443830.html
        # if text = 'Tablet Developer' and TKK = '435102.3120524463',then tk = '315066.159012'

        def RL(a,b):
            for d in range(0,3):
                c = b[d + 2]
                c = ord(c[0]) - 87 if 'a' <= c else int(c)
                c = a >> c if '+' == b[d + 1] else a << c
                a = a + c & 4294967295 if '+' == b[d] else a ^ c
            return a

        g = []
        f = 0
        while f < len(a):
            c = ord(a[f])
            if 128 > c:
                g.append(c)
            else:
                if 2048 > c:
                    g.append((c >> 6) | 192)
                else:
                    if (55296 == (c & 64512)) and (f + 1 < len(a)) and (56320 == (ord(a[f+1]) & 64512)):
                        f += 1
                        c = 65536 + ((c & 1023) << 10) + (ord(a[f]) & 1023)
                        g.append((c >> 18) | 240)
                        g.append((c >> 12) & 63 | 128)
                    else:
                        g.append((c >> 12) | 224)
                        g.append((c >> 6) & 63 | 128)
                g.append((c & 63) | 128)
            f += 1

        e = TKK.split('.')
        h = int(e[0]) or 0
        t = h
        for item in g:
            t += item
            t = RL(t,'+-a^+6')
        t = RL(t,'+-3^+b+-f')
        t ^= int(e[1]) or 0
        if 0 > t:
            t = (t & 2147483647) + 2147483648
        result = t % 1000000
        return str(result) + '.' + str(result ^ h)


    def translate(self,text):
        if time.time() > self.__googleTokenKeyRetireTime:
            self.__updateGoogleTokenKey()
        data = {'q': text}
        self._params['tk'] = self.__getGoogleToken(text,self.__googleTokenKey)
        result = ''
        try:
            res = requests.post(self._url,headers = self._headers,cookies = self.__cookies,data = data,params = self._params,timeout = 6)
            res.raise_for_status()
            jsonText = res.text
            if len(jsonText)>0:
                jsonResult = json.loads(jsonText)
                if len(jsonResult[0])>0:
                    for item in jsonResult[0]:
                        result += item[0]
            return result
        except Exception as ex:
            print('ERROR: ' + str(ex))
            return ''


import time
from GoogleTranslator import GoogleTranslator

def readFile(fileName):
    with open(fileName,'r') as f:
        paragraph = ''
        for line in f:
            if line[0]!='n':
                paragraph += line.strip('n')
            else:
                if len(paragraph)>0:
                    yield paragraph
                    paragraph = ''
        if len(paragraph)>0:
            yield paragraph

main.py：

def main():
    translator = GoogleTranslator()
    count = 0
    with open('C:dxpythond.txt','w',encoding='utf-8') as df:
        for line in readFile('C:dxpythons.txt'):
            if len(line) > 1:
                count += 1
                print('r' + str(count),end = '',flush = True)
                df.write(line.strip() + "n")
                result = translator.translate(line)
                df.write(result.strip() + "nn")

if __name__ == "__main__":
    startTime = time.time()
    main()
    print()
    print('%.2f seconds' % (time.time() - startTime))

结束语

求人不如求己。不能怕烦，代码都是人敲出来的，找不到现成的还得靠自己编。