爬取百度百科词条“猪八戒”及副标题

lzb1001

import urllib.request
import urllib.parse
import re
from bs4 import BeautifulSoup

def main():
    keyword = input('请输入关键词：')
    keyword = urllib.parse.urlencode({'word':keyword}) # 看不懂
    response = urllib.request.urlopen('http://baike.baidu.com/search/word?%s' % keyword) # 此行代码中的word、keyword与上面两行代码有关？
    html = response.read()
    soup = BeautifulSoup(html, 'html.parser')

    for each in soup.find_all(href = re.compile('item')):
        content = ''.join([each.text])  # 看不懂
        url2 = ''.join(['http://baike.baidu.com', each['href']])  # 看不懂
        response2 = urllib.request.urlopen(url2)
        html2 = response2.read()
        soup2 = BeautifulSoup(html2, 'html.parser')
        if soup2.h2:
            content = ''.join([content, soup2.h2.text])  # 看不懂
        content = ''.join([content, '->', url2]) # 看不懂
        print(content)

if __name__ == '__main__':
    main()

【问题】：
1、无法正常运行获得结果
2、很多地方没看懂，尤其标注#的地方看不懂，可否帮忙加下注解，最好逐行
3、url、html、soup、h没看到有0或1，为何使用url2、html2、soup2、h2

特发帖求助

wp231957

无法看懂就对了，记着，提问一定要问能正确运行的代码
你比如说我想问1+1为什么等于3   这谁能回答？？？

lzb1001

import urllib.request
import urllib.parse
import re
from bs4 import BeautifulSoup

def main():
    keyword = input('请输入检索关键词：')
    param = urllib.parse.urlencode({'word':keyword}) # word=%E7%8C%AA%E5%85%AB%E6%88%92
    url = 'https://baike.baidu.com/search/word?%s' % param # [5:]->%E7%8C%AA%E5%85%AB%E6%88%92
    #url = 'https://baike.baidu.com/item/%s' % param[5:]

    #headers={'User-Agent':'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36'} # 可隐藏headers???

    req = urllib.request.Request(url)
    response = urllib.request.urlopen(req)
    html = response.read().decode('utf-8')
    soup = BeautifulSoup(html, 'html.parser')

    for each in soup.find_all(href = re.compile('item'))[5:-1]:
        content = ''.join([each.text])
        url2 = ''.join(['http://baike.baidu.com', each['href'] if "%" in each['href'] else urllib.parse.quote(each['href'])])
        req2 = urllib.request.Request(url2)
        response2 = urllib.request.urlopen(req2)
        html2 = response2.read().decode('utf-8')
        soup2 = BeautifulSoup(html2, 'html.parser')
        if soup2.h2:
            content = ''.join([content, soup2.h2.text])
        content = ''.join([content, ' -> ', url2])
        print(content)

if __name__ == '__main__':
    main()


问题：
1、上面两个URL好像都可以，为什么会这样？主要应该看哪里用哪个呢？
2、用了列表分片[5:-1]后，仅过滤最后一条无用记录，开头几条无法过滤，若不用列表分片或仅用[:-1]还会报错无法运行，这是为什么？
3、如果要加入伪装的header，上述headers用法是否正确？
4、输入关键词“黄埔军校”，刚开始正常抓取，快结束时会报错，不知道什么原因

lzb1001

【四个问题】

1、下面两个URL好像都可以，为什么会这样？主要应该看哪里用哪个呢？
url = '……/search/word?%s' % param
url = '……/item/%s' % param[5:]

2、用了列表分片[5:-1]后，仅过滤最后一条无用记录，开头几条无法过滤；若不用列表分片或仅用[:-1]还会报错无法运行，这是为什么？

3、如果要加入伪装的header，上述headers用法是否正确？
headers={'User-Agent':'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36'}

4、输入关键词“黄埔军校”，刚开始正常抓取，快结束时会报如下错误，不知道什么原因
Traceback (most recent call last):
  File "C:\Users\dell\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 1319, in do_open
    encode_chunked=req.has_header('Transfer-encoding'))
  File "C:\Users\dell\AppData\Local\Programs\Python\Python37\lib\http\client.py", line 1252, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "C:\Users\dell\AppData\Local\Programs\Python\Python37\lib\http\client.py", line 1298, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "C:\Users\dell\AppData\Local\Programs\Python\Python37\lib\http\client.py", line 1247, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "C:\Users\dell\AppData\Local\Programs\Python\Python37\lib\http\client.py", line 1026, in _send_output
    self.send(msg)
  File "C:\Users\dell\AppData\Local\Programs\Python\Python37\lib\http\client.py", line 966, in send
    self.connect()
  File "C:\Users\dell\AppData\Local\Programs\Python\Python37\lib\http\client.py", line 938, in connect
    (self.host,self.port), self.timeout, self.source_address)
  File "C:\Users\dell\AppData\Local\Programs\Python\Python37\lib\socket.py", line 707, in create_connection
    for res in getaddrinfo(host, port, 0, SOCK_STREAM):
  File "C:\Users\dell\AppData\Local\Programs\Python\Python37\lib\socket.py", line 752, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno 11001] getaddrinfo failed

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "D:\work\p14_92.py", line 35, in <module>
    main()
  File "D:\work\p14_92.py", line 26, in main
    response2 = urllib.request.urlopen(req2)
  File "C:\Users\dell\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 222, in urlopen
    return opener.open(url, data, timeout)
  File "C:\Users\dell\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 525, in open
    response = self._open(req, data)
  File "C:\Users\dell\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 543, in _open
    '_open', req)
  File "C:\Users\dell\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 503, in _call_chain
    result = func(*args)
  File "C:\Users\dell\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 1347, in http_open
    return self.do_open(http.client.HTTPConnection, req)
  File "C:\Users\dell\AppData\Local\Programs\Python\Python37\lib\urllib\request.py", line 1321, in do_open
    raise URLError(err)
urllib.error.URLError: <urlopen error [Errno 11001] getaddrinfo failed>