python 使用 lxml.etree.HTML.xpath 解析网页不完整

àì夳堔傛蜴生んèń 2023-05-29 03:24 211阅读 0赞

## 问题 ##

**个人遇到问题，参考性可能不大**

网址：[https://trains.ctrip.com/trainbooking/TrainSchedule/D677/][https_trains.ctrip.com_trainbooking_TrainSchedule_D677]  
今天爬取携程火车车次信息，开始运行结果好好的，但是运行到这里时出现了错误，报错是超出列表范围。

我仔细查看发现是：lxml.etree.HTML.xpath 解析网页不完整，网页明明有 8 个数据，结果只能读取 7 个数据，且 第七个数据不能解析，结果只能返回 6 个数据，程序终止。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70]![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70 1]

## 解决 ##

**1、尝试**  
我想了一上午都没想出来，试了很多办法：

1.  仔细检查路径，改为绝对路径，查看是否要tbody，还是不行。
2.  查看HTML是否能下载完全，发现能够得到完全HTML。

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70 2]

**2、解决**  
最后无意将HTML加载格式改了一下，竟然问题解决了，原来我习惯以二进制解析 **res.content** ，解析速度快，**无意改成文本解 res.text 析问题解决了**，可能是解析长度问题吧。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70 3]

## 总结 ##

**声明这个不是解析不出来，而是解析不完整。**  
在解决这个问题查找了很久，也遇到很多类似的问题

**xpath解析不到数据**  
（1）可能是路径出问题了  
（2）如果用谷歌直接提取 **full xpath**，可能是浏览器渲染问题，浏览器会给表格添加一个 tbody ，本来没有的，所以需要去掉  
（3）其实最好根据下载下来的 HTML，一步一步的查看，不过麻烦。（出问题了在这样，平时提取一般没问题）

代码

# !/usr/bin/python
    # -*- coding: utf-8 -*-
    # @Time : 2019/11/1 17:55 
    # @Author : ljf
    # @File : train_number.py
    import random
    import time
    import re
    import requests
    from lxml import etree
    import mysql
    
    
    def TrainNumber(code, path):
        """
        Args:
            code:   修改车次
            path:   保存路径
    
        Returns:    无
        """
        url = "https://trains.ctrip.com/trainbooking/TrainSchedule/{}/".format(code)
        headers = {
        
            "Host": "trains.ctrip.com",
            "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:70.0) Gecko/20100101 Firefox/70.0",
            "Referer": "https://trains.ctrip.com/trainbooking/TrainSchedule",
            "Connection": "close",
        }
        res = requests.get(url, headers=headers)
        res.encoding = 'GBK'
    
        f = open(path, 'a+')
        f.write(code + '\n')
        if res.status_code == 200:
            # 以文本解析，二进制解析快但是会少一些数据出问题
            xmlContent = etree.HTML(res.text)
            trs = xmlContent.xpath("/html/body/ul/li/form/div[4]/div/div/div[1]/div[3]/table[2]/tbody/tr")
            if trs:
                for tr in trs:
                    number = tr.xpath("./td[2]/text()")
                    number = re.findall(r'\d+', str(number))[0]
    
                    station_name = tr.xpath("./td[3]/a/text()")[0]
    
                    arrival_time = tr.xpath("td[4]/text()")
                    arrival_time = re.findall('[0-9]{2}:[0-9]{2}', str(arrival_time))
                    if arrival_time:
                        arrival_time = arrival_time[0]
                    else:
                        arrival_time = ""
    
                    depart_time = tr.xpath("td[5]/text()")
                    depart_time = re.findall('[0-9]{2}:[0-9]{2}', str(depart_time))[0]
    
                    info = [number, station_name, arrival_time, depart_time]
                    f.write(str(info) + '\n')
                    print(info)
        f.write('\n')
        f.close()
    
    
    def start():
        """
        条件准备
        """
        number_path = "./Train_NumberInfo.txt"
        sql = "SELECT code FROM t_number"
        codes = mysql.mysql_select_12306(sql)
        num = len(codes)
        for i in range(0, num):
            code = codes[i][0]
            try:
                TrainNumber(code, number_path)
                print("{} 车次下载完毕！".format(codes[i][0]))
            except Exception as e:
                print(e)
            finally:
                # 随机延时4~8秒
                time.sleep(random.randint(4, 8))
    
    
    if __name__ == "__main__":
        start()

[https_trains.ctrip.com_trainbooking_TrainSchedule_D677]: https://trains.ctrip.com/trainbooking/TrainSchedule/D677/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20191102230343584.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20191102230453485.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20191102231939758.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70 3]: https://img-blog.csdnimg.cn/20191102231842707.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg==,size_16,color_FFFFFF,t_70