Python txt文件标签解析

Question

我正在尝试解析 txt 文件中两个不同标签的内容，并且我获取了第一个标签“p”的所有实例，但没有获取第二个“l”的实例。是“或”有问题吗？

感谢您的帮助。这是我正在使用的代码

with open('standardA00456.txt','w') as output_file:
    with open('standardA00456.txt','r') as open_file:
            the_whole_file = open_file.read()
            start_position = 0

            while True:

               start_position = the_whole_file.find('<p>' or '<l>', start_position)

               end_position = the_whole_file.find('</p>' or '</l>', start_position)
               data = the_whole_file[start_position:end_position+5]


               output_file.write(data + "\n")
               start_position = end_position

Answer 1

'<p>' or '<l>' 将始终等于 '<p>' ，因为它告诉 Python 仅当 '<l>' 为 '<p>' 、 None 、数字零或空时才使用 False 。由于字符串 '<p>' 从来都不是其中之一，因此始终会跳过 '<l>':

>>> '<p>' or '<l>'
'<p>'
>>> None or '<l>'
'<l>'

相反，您可以轻松地使用 re.findall :

import re
with open('standardA00456.txt','w') as out_f,  open('standardA00456.txt','r') as open_f:
    p_or_ls = re.findall(r'(?:<p>.*?</p>)|(?:<l>.*?</l>)', 
                         open_f.read(), 
                         flags=re.DOTALL) #to include newline characters
    for p_or_l in p_or_ls:
        out_f.write(p_or_l + "\n")

但是，使用正则表达式解析带有标签(例如 HTML 和 XML)的文件是 not a good idea 。使用模块，例如 BeautifulSoup 更安全:

from bs4 import BeautifulSoup
with open('standardA00456.txt','w') as out_f,  open('standardA00456.txt','r') as open_f:
    soup = BeautifulSoup(open_f.read())
    for p_or_l in soup.find_all(["p", "l"]):
        out_f.write(p_or_l + "\n")