百度翻译爬虫-Web版(自动生成sign)

# 面向对象
# 百度翻译 -- 网页版(自动获取token,sign)
import requests
import js2py
import json
import re


class WebFanyi:
    """百度翻译网页版爬虫"""
    def __init__(self,query_str):
        self.session = requests.session()
        headers = {
            "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.121 Safari/537.36",
        }
        self.session.headers = headers
        self.baidu_url = "https://www.baidu.com/"
        self.root_url = "https://fanyi.baidu.com/"
        self.lang_url = "https://fanyi.baidu.com/langdetect"
        self.trans_url = "https://fanyi.baidu.com/v2transapi"
        self.query_str = query_str

    def get_token_gtk(self):
        '''获取token和gtk(用于合成Sign)'''
        self.session.get(self.root_url)
        resp = self.session.get(self.root_url)
        html_str = resp.content.decode()
        token = re.findall(r"token: '(.*?)'", html_str)[0]
        gtk = re.findall(r"window.gtk = '(.*?)'", html_str)[0]
        return token,gtk

    def generate_sign(self,gtk):
        """生成sign"""
        # 1. 准备js编译环境
        context = js2py.EvalJs()
        with open('webtrans.js', encoding='utf8') as f:
            js_data = f.read()
            js_data = re.sub("window\[l\]",'"'+gtk+'"',js_data)
            # js_data = re.sub("window\[l\]", "\"{}\"".format(gtk), js_data)
            # print(js_data)
            context.execute(js_data)
        sign = context.e(self.query_str)
        return sign

    def lang_detect(self):
        '''获取语言转换类型.eg: zh-->en'''
        lang_resp = self.session.post(self.lang_url,data={"query":self.query_str})
        lang_json_str = lang_resp.content.decode()  # {"error":0,"msg":"success","lan":"zh"}
        lan = json.loads(lang_json_str)['lan']
        to = "en" if lan == "zh" else "zh"
        return lan,to


    def parse_url(self,post_data):
        trans_resp = self.session.post(self.trans_url,data=post_data)
        trans_json_str = trans_resp.content.decode()
        trans_json = json.loads(trans_json_str)
        result = trans_json["trans_result"]["data"][0]["dst"]
        print("{}: {}".format(self.query_str,result))

    def run(self):
        """实现逻辑"""
        # 1.获取百度的cookie,(缺乏百度首页的cookie会始终报错998)
        self.session.get(self.baidu_url)
        # 2. 获取百度翻译的token和gtk(用于合成sign)
        token, gtk = self.get_token_gtk()
        # 3. 生成sign
        sign = self.generate_sign(gtk)
        # 4. 获取语言转换类型.eg: zh-->en
        lan, to = self.lang_detect()
        # 5. 发送请求,获取响应,输出结果
        post_data = {
            "from": lan,
            "to": to,
            "query": self.query_str,
            "transtype": "realtime",
            "simple_means_flag": 3,
            "sign": sign,
            "token": token
        }
        self.parse_url(post_data)

if __name__ == '__main__':
    webfanyi = WebFanyi('lover')
    webfanyi.run()

上述代码中用于生成sign的 webtrans.js 文件具体代码如下(可以自己抓包,在js中打断点获取):

// webtrans.js

function n(r, o) {
    for (var t = 0; t < o.length - 2; t += 3) {
        var a = o.charAt(t + 2);
        a = a >= "a" ? a.charCodeAt(0) - 87 : Number(a),
        a = "+" === o.charAt(t + 1) ? r >>> a : r << a,
        r = "+" === o.charAt(t) ? r + a & 4294967295 : r ^ a
    }
    return r
}
function e(r) {
    var o = r.match(/[\uD800-\uDBFF][\uDC00-\uDFFF]/g);
    if (null === o) {
        var t = r.length;
        t > 30 && (r = "" + r.substr(0, 10) + r.substr(Math.floor(t / 2) - 5, 10) + r.substr(-10, 10))
    } else {
        for (var e = r.split(/[\uD800-\uDBFF][\uDC00-\uDFFF]/), C = 0, h = e.length, f = []; h > C; C++)
            "" !== e[C] && f.push.apply(f, a(e[C].split(""))),
            C !== h - 1 && f.push(o[C]);
        var g = f.length;
        g > 30 && (r = f.slice(0, 10).join("") + f.slice(Math.floor(g / 2) - 5, Math.floor(g / 2) + 5).join("") + f.slice(-10).join(""))
    }
    var u = void 0
      ,
        // l = "" + String.fromCharCode(103) + String.fromCharCode(116) + String.fromCharCode(107);
        i = null;
        u = null !== i ? i : (i = window[l] || "") || "";
    for (var d = u.split("."), m = Number(d[0]) || 0, s = Number(d[1]) || 0, S = [], c = 0, v = 0; v < r.length; v++) {
        var A = r.charCodeAt(v);
        128 > A ? S[c++] = A : (2048 > A ? S[c++] = A >> 6 | 192 : (55296 === (64512 & A) && v + 1 < r.length && 56320 === (64512 & r.charCodeAt(v + 1)) ? (A = 65536 + ((1023 & A) << 10) + (1023 & r.charCodeAt(++v)),
        S[c++] = A >> 18 | 240,
        S[c++] = A >> 12 & 63 | 128) : S[c++] = A >> 12 | 224,
        S[c++] = A >> 6 & 63 | 128),
        S[c++] = 63 & A | 128)
    }
    for (var p = m, F = "" + String.fromCharCode(43) + String.fromCharCode(45) + String.fromCharCode(97) + ("" + String.fromCharCode(94) + String.fromCharCode(43) + String.fromCharCode(54)), D = "" + String.fromCharCode(43) + String.fromCharCode(45) + String.fromCharCode(51) + ("" + String.fromCharCode(94) + String.fromCharCode(43) + String.fromCharCode(98)) + ("" + String.fromCharCode(43) + String.fromCharCode(45) + String.fromCharCode(102)), b = 0; b < S.length; b++)
        p += S[b],
        p = n(p, F);
    return p = n(p, D),
    p ^= s,
    0 > p && (p = (2147483647 & p) + 2147483648),
    p %= 1e6,
    p.toString() + "." + (p ^ m)
}

实际上,除了用js2py作为python中执行js代码的环境编译器外,还可以使用另一个方法 'execjs' ,不过要先通过 pip install PyExecJS 安装PyExecJS模块.具体实现代码如下:

import execjs
with open("webtrans.js") as f:
    js_data = f.read()
    js_data = re.sub("window\[l\]", '"' + gtk + '"', js_data)
    sign = execjs.compile(js_data).call("e", query_str)  # 调用webtrans.js代码中的 e函数，传入参数为 query_str
    print(sign)