python爬取Google翻译

请求分析

首先，我们打开开发者工具，然后打开Google翻译(translate.google.cn)，

我们过滤器选择JS，发现第一个js就很可疑，先记下来。
接着，我们随便输入一些内容，便可以很轻松地抓取到这个请求：

观察GET参数，不用说都能看出来下面几个参数是重要的参数：

我们可以猜测：sl为源语言，tl为目标语言，q为要翻译的内容，tk为某种验证参数。
那么tk参数如何获得呢？

tk参数获取

打开我们最开始发现的那个js文件：
translate.google.cn/translate/releases/twsfe_w_20200622_RC00/r/js/translate_m_zh-CN.js
将其格式化，再经过漫长的搜寻，找到了下面的一串代码：

var pu = function(a) {
    return function() {
        return a
    }
},
qu = function(a, b) {
    for (var c = 0; c < b.length - 2; c += 3) {
        var d = b.charAt(c + 2);
        d = "a" <= d ? d.charCodeAt(0) - 87 : Number(d);
        d = "+" == b.charAt(c + 1) ? a >>> d: a << d;
        a = "+" == b.charAt(c) ? a + d & 4294967295 : a ^ d
    }
    return a
},
ru = null,
su = function(a) {
    if (null !== ru) var b = ru;
    else {
        b = pu(String.fromCharCode(84));
        var c = pu(String.fromCharCode(75));
        b = [b(), b()];
        b[1] = c();
        b = (ru = window[b.join(c())] || "") || ""
    }
    var d = pu(String.fromCharCode(116));
    c = pu(String.fromCharCode(107));
    d = [d(), d()];
    d[1] = c();
    c = "&" + d.join("") + "=";
    d = b.split(".");
    b = Number(d[0]) || 0;
    for (var e = [], f = 0, g = 0; g < a.length; g++) {
        var h = a.charCodeAt(g);
        128 > h ? e[f++] = h: (2048 > h ? e[f++] = h >> 6 | 192 : (55296 == (h & 64512) && g + 1 < a.length && 56320 == (a.charCodeAt(g + 1) & 64512) ? (h = 65536 + ((h & 1023) << 10) + (a.charCodeAt(++g) & 1023), e[f++] = h >> 18 | 240, e[f++] = h >> 12 & 63 | 128) : e[f++] = h >> 12 | 224, e[f++] = h >> 6 & 63 | 128), e[f++] = h & 63 | 128)
    }
    a = b;
    for (f = 0; f < e.length; f++) a += e[f],
    a = qu(a, "+-a^+6");
    a = qu(a, "+-3^+b+-f");
    a ^= Number(d[1]) || 0;
    0 > a && (a = (a & 2147483647) + 2147483648);
    a %= 1E6;
    return c + (a.toString() + "." + (a ^ b))
};

很明显，这段代码是一段算法，而且是经过混淆的(变量名很奇怪)。
经过验证，这就是tk参数的加密算法。把不需要部分的去除，稍微进行整理一下：

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

这里的tkk就在源代码里面可以找到，如下图：

execjs库的调用

接下来，我们用python的execjs库进行测试，如果没有安装请使用pip install PyExecJS进行安装。

import execjs

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

print(a.call("su",'test','442788.2585626513')) #获取tk

我们将运行得到的tk带入那个GET请求中，发现仍然可以正常得到返回json，说明tk获取成功。
于是我们就可以通过修改GET请求的参数实现获取翻译结果了。

python版算法

execjs的性能并不是很好，执行时间会很长。因此我们采用另一种方法：将js转换成python代码。
转换后大致代码如下：

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)

最终代码

import requests,re,json,time

class GoogleTranslator():
    _host = 'translate.google.cn'
    _headers = {
        'Host': _host,
        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.0',
        'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
        'Accept-Language': 'zh-CN,zh;q=0.9,en;q=0.8,en-GB;q=0.7,en-US;q=0.6',
        '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'
    }
    _url = 'https://' + _host + '/translate_a/single'
    _params = { #除关键参数，其它参数直接复制过来就行了
            '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 = ''
    __googleTokenKeyUpdataTime = 600.0
    __googleTokenKeyRetireTime = time.time() + 600.0

    def __init__(self, src = 'auto', dest = 'zh-CN', tkkUpdataTime = 600.0):
        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):
        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) #自动从源代码中获取tkk，或者这里改成一个定值也可以
        except requests.exceptions.ReadTimeout as ex:
            print('ERROR: ' + str(ex))
            time.sleep(1)
        return result

    def __getGoogleToken(self, a, TKK): #获取tk
        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)


    def translate(self, text): #获取返回的json中的结果
        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
            #print(jsonText)
            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 ''

def Translate(text,to):
    translator = GoogleTranslator(dest=to)
    result = translator.translate(text)
    return result

print(Translate(input(': '),'zh-CN')) #自动检测语言到中文翻译

以上代码只是获取了翻译结果，在返回的json中其实还包含了很多其它的信息，可以自行扩展此代码。
最后，附上语言对应的代码(sl和tl所用)：

source_code_name: [{
    code: 'auto',
    name: '自动检测语言'
},
{
    code: 'sq',
    name: '阿尔巴尼亚语'
},
{
    code: 'ar',
    name: '阿拉伯语'
},
{
    code: 'am',
    name: '阿姆哈拉语'
},
{
    code: 'az',
    name: '阿塞拜疆语'
},
{
    code: 'ga',
    name: '爱尔兰语'
},
{
    code: 'et',
    name: '爱沙尼亚语'
},
{
    code: 'or',
    name: '奥里亚语(奥里亚文)'
},
{
    code: 'eu',
    name: '巴斯克语'
},
{
    code: 'be',
    name: '白俄罗斯语'
},
{
    code: 'bg',
    name: '保加利亚语'
},
{
    code: 'is',
    name: '冰岛语'
},
{
    code: 'pl',
    name: '波兰语'
},
{
    code: 'bs',
    name: '波斯尼亚语'
},
{
    code: 'fa',
    name: '波斯语'
},
{
    code: 'af',
    name: '布尔语(南非荷兰语)'
},
{
    code: 'tt',
    name: '鞑靼语'
},
{
    code: 'da',
    name: '丹麦语'
},
{
    code: 'de',
    name: '德语'
},
{
    code: 'ru',
    name: '俄语'
},
{
    code: 'fr',
    name: '法语'
},
{
    code: 'tl',
    name: '菲律宾语'
},
{
    code: 'fi',
    name: '芬兰语'
},
{
    code: 'fy',
    name: '弗里西语'
},
{
    code: 'km',
    name: '高棉语'
},
{
    code: 'ka',
    name: '格鲁吉亚语'
},
{
    code: 'gu',
    name: '古吉拉特语'
},
{
    code: 'kk',
    name: '哈萨克语'
},
{
    code: 'ht',
    name: '海地克里奥尔语'
},
{
    code: 'ko',
    name: '韩语'
},
{
    code: 'ha',
    name: '豪萨语'
},
{
    code: 'nl',
    name: '荷兰语'
},
{
    code: 'ky',
    name: '吉尔吉斯语'
},
{
    code: 'gl',
    name: '加利西亚语'
},
{
    code: 'ca',
    name: '加泰罗尼亚语'
},
{
    code: 'cs',
    name: '捷克语'
},
{
    code: 'kn',
    name: '卡纳达语'
},
{
    code: 'co',
    name: '科西嘉语'
},
{
    code: 'hr',
    name: '克罗地亚语'
},
{
    code: 'ku',
    name: '库尔德语'
},
{
    code: 'la',
    name: '拉丁语'
},
{
    code: 'lv',
    name: '拉脱维亚语'
},
{
    code: 'lo',
    name: '老挝语'
},
{
    code: 'lt',
    name: '立陶宛语'
},
{
    code: 'lb',
    name: '卢森堡语'
},
{
    code: 'rw',
    name: '卢旺达语'
},
{
    code: 'ro',
    name: '罗马尼亚语'
},
{
    code: 'mg',
    name: '马尔加什语'
},
{
    code: 'mt',
    name: '马耳他语'
},
{
    code: 'mr',
    name: '马拉地语'
},
{
    code: 'ml',
    name: '马拉雅拉姆语'
},
{
    code: 'ms',
    name: '马来语'
},
{
    code: 'mk',
    name: '马其顿语'
},
{
    code: 'mi',
    name: '毛利语'
},
{
    code: 'mn',
    name: '蒙古语'
},
{
    code: 'bn',
    name: '孟加拉语'
},
{
    code: 'my',
    name: '缅甸语'
},
{
    code: 'hmn',
    name: '苗语'
},
{
    code: 'xh',
    name: '南非科萨语'
},
{
    code: 'zu',
    name: '南非祖鲁语'
},
{
    code: 'ne',
    name: '尼泊尔语'
},
{
    code: 'no',
    name: '挪威语'
},
{
    code: 'pa',
    name: '旁遮普语'
},
{
    code: 'pt',
    name: '葡萄牙语'
},
{
    code: 'ps',
    name: '普什图语'
},
{
    code: 'ny',
    name: '齐切瓦语'
},
{
    code: 'ja',
    name: '日语'
},
{
    code: 'sv',
    name: '瑞典语'
},
{
    code: 'sm',
    name: '萨摩亚语'
},
{
    code: 'sr',
    name: '塞尔维亚语'
},
{
    code: 'st',
    name: '塞索托语'
},
{
    code: 'si',
    name: '僧伽罗语'
},
{
    code: 'eo',
    name: '世界语'
},
{
    code: 'sk',
    name: '斯洛伐克语'
},
{
    code: 'sl',
    name: '斯洛文尼亚语'
},
{
    code: 'sw',
    name: '斯瓦希里语'
},
{
    code: 'gd',
    name: '苏格兰盖尔语'
},
{
    code: 'ceb',
    name: '宿务语'
},
{
    code: 'so',
    name: '索马里语'
},
{
    code: 'tg',
    name: '塔吉克语'
},
{
    code: 'te',
    name: '泰卢固语'
},
{
    code: 'ta',
    name: '泰米尔语'
},
{
    code: 'th',
    name: '泰语'
},
{
    code: 'tr',
    name: '土耳其语'
},
{
    code: 'tk',
    name: '土库曼语'
},
{
    code: 'cy',
    name: '威尔士语'
},
{
    code: 'ug',
    name: '维吾尔语'
},
{
    code: 'ur',
    name: '乌尔都语'
},
{
    code: 'uk',
    name: '乌克兰语'
},
{
    code: 'uz',
    name: '乌兹别克语'
},
{
    code: 'es',
    name: '西班牙语'
},
{
    code: 'iw',
    name: '希伯来语'
},
{
    code: 'el',
    name: '希腊语'
},
{
    code: 'haw',
    name: '夏威夷语'
},
{
    code: 'sd',
    name: '信德语'
},
{
    code: 'hu',
    name: '匈牙利语'
},
{
    code: 'sn',
    name: '修纳语'
},
{
    code: 'hy',
    name: '亚美尼亚语'
},
{
    code: 'ig',
    name: '伊博语'
},
{
    code: 'it',
    name: '意大利语'
},
{
    code: 'yi',
    name: '意第绪语'
},
{
    code: 'hi',
    name: '印地语'
},
{
    code: 'su',
    name: '印尼巽他语'
},
{
    code: 'id',
    name: '印尼语'
},
{
    code: 'jw',
    name: '印尼爪哇语'
},
{
    code: 'en',
    name: '英语'
},
{
    code: 'yo',
    name: '约鲁巴语'
},
{
    code: 'vi',
    name: '越南语'
},
{
    code: 'zh-CN',
    name: '中文'
}]