python 爬虫问题求教望解答疑惑

Question

import requests
from bs4 import BeautifulSoup
def html(url):
    resp=requests.get(url)
    soup=BeautifulSoup(resp.text,'html.parser')
    code_tag=soup.new_tag("code")
    pres=soup.find_all("pre")
    for s in pres:
        s.string.wrap(code_tag)
    print(pres)
    
html('https://www.cnblogs.com/wind666/p/11992837.html')

返回结果

[<pre></pre>, <pre></pre>, <pre></pre>, <pre><code># 想得到1-10的平方组成的list
list_1_10 = [x**2 for x in range(1,11)]
print(list_1_10)# 想得到1-10中为偶数的平方组成的list
example = [i**2 for i in range(1,11) if i%2 == 0 ]
print(example)# 想得到多重嵌套中的数是2的倍数的平方组成的list
example2 = [[1,2,3],[4,5,6],[7,8,9],[10]]
example3 = [j**2 for i in example2 for j in i if j%2 == 0]
print(example3)# 想得到多重嵌套的list中一重嵌套中list长度大于1的list中的数为2的倍数的平方组成的list
example4 = [[1,2,3],[4,5,6],[7,8,9],[10]]
exmaple5 = [j**2 for i in example2 if len(i)&gt;1 for j in i if j%2 == 0]
print(exmaple5)</code></pre>]

请问大神为何前几个pre标签都没添加code标签只有最后一个添加了code标签,前几个pre标签内字符串被删除了，明明for循环遍历操作了，希望大神能够解答，谢谢！

Answer 1

def html(url):
    resp = requests.get(url)
    soup = BeautifulSoup(resp.text, 'html.parser')
    # code_tag = soup.new_tag("code") 问题在这
    pres = soup.find_all("pre")
    for s in pres:
        s.string.wrap(soup.new_tag("code"))
    print(repr(pres))

---

分析：

s.string的类型为 bs4.element.NavigableString。

def wrap(self, wrap_inside):
    """
    Wrap this PageElement inside another one.
    :param wrap_inside: A PageElement. 
    :return: `wrap_inside`, occupying the position in the tree that used to be occupied by `self`, and with `self` inside it. 
    """ 
    me = self.replace_with(wrap_inside)
    wrap_inside.append(me)
    return wrap_inside

当执行完wrap操作，code_tag已被修改。