如何将含break的Python for循环转为无break的while循环？

这段代码里的break语句让我头疼，研究了半天，想问问有没有符合Python风格的方法把它改成while循环，核心是要移除break。我正在练习设计更高效的循环。

原代码如下：

import re

file = open('parse.txt', 'r')
html = file.readlines()

def cleanup():
    result = []
    for line in html:
        if "<li" and "</li>" in line:
            stripped = re.sub(r'[\n\t]*<[^<]+?>', '', line).rstrip()
            quoted = f'"{stripped}"'
            result.append(quoted)
        elif "INSTRUCTIONS" in line:
            break
    return ",\n".join(result)

附parse.txt内容：

<p style="text-align:justify"><strong><span style="background-color:#ecf0f1">INGREDIENTS</span></strong></p>

    <li style="text-align:justify"><span style="background-color:#ecf0f1">3 lb ground beef (80/20)</span></li>
<ul>
    <li style="text-align:justify"><span style="background-color:#ecf0f1">1 large onion, chopped</span></li>
    <li style="text-align:justify"><span style="background-color:#ecf0f1">2-3 cloves garlic, minced</span></li>
    <li style="text-align:justify"><span style="background-color:#ecf0f1">2 jalapeño peppers, roasted, peeled, de-seeded, chopped</span></li>
    <li style="text-align:justify"><span style="background-color:#ecf0f1">4-5 roma tomatoes, roasted peeled, chopped</span></li>
    <li style="text-align:justify"><span style="background-color:#ecf0f1">1 15 oz can kidney beans, strained and washed</span></li>
    <li style="text-align:justify"><span style="background-color:#ecf0f1">2 tsp salt</span></li>
    <li style="text-align:justify"><span style="background-color:#ecf0f1">2 tsp black pepper</span></li>
    <li style="text-align:justify"><span style="background-color:#ecf0f1">2 tsp cumin</span></li>
    <li style="text-align:justify"><span style="background-color:#ecf0f1">¼ - ½ tsp cayenne pepper</span></li>
    <li style="text-align:justify"><span style="background-color:#ecf0f1">1 tsp garlic powder</span></li>
    <li style="text-align:justify"><span style="background-color:#ecf0f1">1 tsp Mexican oregano</span></li>
    <li style="text-align:justify"><span style="background-color:#ecf0f1">1 tsp paprika</span></li>
    <li style="text-align:justify"><span style="background-color:#ecf0f1">1 tsp smoked paprika</span></li>
    <li style="text-align:justify"><span style="background-color:#ecf0f1">3 cups chicken broth</span></li>
    <li style="text-align:justify"><span style="background-color:#ecf0f1">2 tbsp tomato paste</span></li>
</ul>

<p style="text-align:justify"><strong>INSTRUCTIONS</strong></p>

<ol>
    <li style="text-align:justify">Heat a large put or Dutch oven over medium-high heat and brown the beef, while stirring to break it up. Cook until no longer pink. Drain out the liquid.</li>
    <li style="text-align:justify">Stir in onions and cook for about 5 minutes until they are pale and soft. Add in minced garlic and jalapeño peppers, stirring for another minute.</li>
    <li style="text-align:justify">Stir in the chopped tomatoes, all the spices, and tomato paste until well-distributed and tomato paste has broken up, then follow with the broth. Allow the pot to come to a gentle boil over medium heat, uncovered for about 20 minutes.</li>
    <li style="text-align:justify">Reduce heat to low, cover and simmer for at least 3 hours, until liquid has reduced.</li>
    <li style="text-align:justify">During the last 20-30 minutes of cook time, add in the kidney beans; uncover and allow liquid to reduce further during this time.</li>
    <li style="text-align:justify">Serve hot with jalapeño cornbread muffins, shredded cheese, avocado chunks, chopped cilantro, chopped green onion, tortilla chips.</li>
</ol>

方法一：转成while循环（彻底移除break） #

你可以用索引控制循环，通过while遍历到"INSTRUCTIONS"行就停下，完全不用break：

import re

file = open('parse.txt', 'r')
html = file.readlines()

def cleanup():
    result = []
    index = 0
    # 只要索引没超范围，且当前行不含INSTRUCTIONS，就继续循环
    while index < len(html) and "INSTRUCTIONS" not in html[index]:
        line = html[index]
        # 原代码的条件判断有bug，这里修正成两个标签都要在该行里
        if "<li" in line and "</li>" in line:
            stripped = re.sub(r'[\n\t]*<[^<]+?>', '', line).rstrip()
            quoted = f'"{stripped}"'
            result.append(quoted)
        index += 1
    return ",\n".join(result)

另外提一句：原代码里if "<li" and "</li>" in line的逻辑有问题，"<li"本身是非空字符串，会被当成True，实际只会判断"</li>"是否在该行，这里帮你修正成两个条件都满足的正确逻辑。

方法二：更Pythonic的写法（不用while也能优雅截断） #

如果不是非要用while，Python里更地道的方式是用迭代器截断，比如itertools.takewhile，直接取到目标行之前的所有内容，代码更简洁：

import re
from itertools import takewhile

file = open('parse.txt', 'r')
html = file.readlines()

def cleanup():
    # 只保留INSTRUCTIONS行之前的所有行
    lines_before_instructions = takewhile(lambda line: "INSTRUCTIONS" not in line, html)
    result = []
    for line in lines_before_instructions:
        if "<li" in line and "</li>" in line:
            stripped = re.sub(r'[\n\t]*<[^<]+?>', '', line).rstrip()
            quoted = f'"{stripped}"'
            result.append(quoted)
    return ",\n".join(result)

这种写法符合Python的迭代思维，不用手动管理索引，可读性更高。

额外优化：文件处理的正确姿势 #

原代码直接open文件没关闭，建议用with上下文管理器，确保文件自动关闭，还能逐行读取省内存：

import re
from itertools import takewhile

def cleanup():
    result = []
    with open('parse.txt', 'r') as file:
        # 逐行读取，碰到INSTRUCTIONS就停止
        lines_before_instructions = takewhile(lambda line: "INSTRUCTIONS" not in line, file)
        for line in lines_before_instructions:
            if "<li" in line and "</li>" in line:
                stripped = re.sub(r'[\n\t]*<[^<]+?>', '', line).rstrip()
                quoted = f'"{stripped}"'
                result.append(quoted)
    return ",\n".join(result)

这样处理大文件也不会占太多内存，还避免了资源泄漏。

内容的提问来源于stack exchange，提问作者Snerd