在 Python 3 中找到特定行后如何跳过 n 行？

Posted 2023-02-25

【中文标题】在 Python 3 中找到特定行后如何跳过 n 行？

【英文标题】：How to skip n number of lines after finding a specific line in Python 3?

【发布时间】：2020-03-09 13:41:55

【问题描述】：

假设我有一个大文本文件，我想跳过包含某个关键字的行以及该行之后的 2 行。

原始文件：

line1 some words
line2 some words
line3 keyword
line4 some words
line5 some words
line6 some words
line7 some words
line8 some words

新文件：

line1 some words
line2 some words
line6 some words
line7 some words
line8 some words

我的代码的简化 sn-p：

with open('Original_file','r') as f:
    lines = f.readlines()
    nf = open('New_file', 'w')
    for line in lines:
        if 'keyword' in line:
            for i in range(3): continue
        else:
            nf.write(line + "\n")

循环“for i in range(3): continue”不会跳过行（我假设是因为它只是在嵌套的 for 循环中继续，而不是“for line in lines”for 循环。我也试过“ next(f)" 而不是 "c​​ontinue" 并收到 StopIteration 错误消息。

当然，如果我尝试，

with open('Original_file','r') as f:
    lines = f.readlines()
    nf = open('New_file', 'w')
    for line in lines:
        if 'keyword' in line: 
            continue
        else:
            nf.write(line + "\n")

它成功跳过了一行，但只跳过了带有关键字的行，而我也想跳过接下来的两行（总共3行）。

感谢任何建议。感谢您的帮助。

【问题讨论】：

您可以使用索引来迭代for i in range(0, len(lines)):，而不是迭代for line in lines:，然后您可以随时增加索引（注意不要通过最后一行！）。

【参考方案1】：

您可以尝试迭代索引而不是元素：

with open('Original_file','r') as f:
    lines = f.readlines()

nf = open('New_file', 'w')
i = 0
while i< len(lines):
    line = lines[i]
    if 'keyword' in line:
        i+=3
    else:
        nf.write(line + "\n")
        i+=1

【参考方案2】：

制作一个计数器并据此跳过行。

with open('Original_file','r') as f:
    lines = f.readlines()
    nf = open('New_file', 'w')
    skip_lines = 0
    for line in lines:
        if skip_lines > 0:
            skip_lines -= 1
        elif 'keyword' in line: 
            skip_lines = 3
        else:
            nf.write(line + "\n")

【参考方案3】：

您可以使用标志 /counter 来实现此目的

with open('Original_file','r') as f:
    lines = f.readlines()
    skip = 0
    nf = open('New_file', 'w')
    for line in lines:
        if skip:
            skip -=1
        elif 'keyword' in line:
            skip = 3
        else:
            nf.write(line + "\n")

【参考方案4】：

问题是您直接从列表中提取行，因此，您无法与for line in lines 使用的底层迭代器进行交互。 您应该简单地将文件对象用作迭代器：

with open('Original_file','r') as f, open('New_file', 'w') as nf
    for line in f:
        if 'keyword' in line:
            for i in range(2): next(f)
        else:
            nf.write(line)

这里唯一的假设是任何包含keyword 的行后面至少有2 行。

【参考方案5】：

你可以使用next()，即：

with open("old.txt") as f, open("new.txt", "w") as w:
  for line in f:
    if "keyword" in line:
      next(f), next(f)
      continue
    w.write(line)

Demo

---

如果你喜欢list comprehension，你也可以使用：

with open("old.txt") as f, open("new.txt", "w") as w:
  [w.write(line) if not "keyword" in line else [next(f) for _ in range(2)] for line in f]

Demo