Question

我试图在Python中的.txt文件中遇到某个短语后删除38行文本，同时仍然打印其余文本。

我目前的代码是

with open('text_file.txt','r') as f:
lines = f.readlines()
for line in lines:
    if "certain_phrase" in line:
        for num in range(38):
            del line
    else:
        print(line,end='')

但是，我一直收到以下错误：

Traceback (most recent call last):
  File "C:\<location of file>\python_program.py", line 6, in <module>
    del line
NameError: name 'line' is not defined

有没有人有任何建议或线索，为什么一旦我把它放在下面的for循环中就不能识别“line”？另外，有没有更好的方法来执行这种程序？

Answer 1

您需要从列表中删除，您不能del该行，最简单的方法是写入临时文件并在您想要修改文件后复制，如果您只想打印忽略38行替换写入打印：

 with open('in.txt','r') as f,open('temp.txt','w') as temp:
    for line in f:
        if "phrase" in line:
            for i in range(38):
                next(f) # skip 38 lines
        else:
            temp.write(line)

然后使用shutil移动文件：

import shutil

shutil.move("temp.txt","in.txt")

您还可以使用NamedTemporaryFile：

from tempfile import NamedTemporaryFile

with open('file.txt','r') as f, NamedTemporaryFile(dir=".",delete=False) as  temp:
    for line in f:
        if "phrase" in line:
            for i in range(38):
                next(f)
        else:
            temp.write(line)

import shutil
shutil.move(temp.name,"file.txt")

我看到的唯一潜在问题是，如果短语位于38个被忽略的行之一中，您还应该从那里删除接下来的38行。

To ignore until a second phrase, keep looping in the inner loop until you find the second phrase then break:

with open('in.txt','r') as f, NamedTemporaryFile(dir=".", delete=False) as temp:
    for line in f:
        if "phrase" in line:
            for _line in f:
                if "phrase2" in _line:
                    break
        else:
            temp.write(line)

Answer 2

不是尝试从文件中删除行，而是根据旧文件写入新文件。以下使用__next__()来跳过生成器产生的line。

with open('text_file.txt','r') as f, open('text_file_mod.txt', 'w') as w:
    for line in f:
        w.write(line)
        if "certain_phrase" in line:
            for num in range(38): # skip 38 lines
                next(f)

如果您是通过交互式解释器执行此操作，则可以通过将next(f)和w.write(line)的结果保存到变量来阻止其吐出返回值。

Answer 3

del line实际上删除了变量line，这意味着当您尝试再次执行此操作时，它不起作用，因为line未定义了。您可以循环索引以查找行，中断，然后删除接下来的38行：

with open('text_file.txt','r') as f:
lines = f.readlines()
for i in range(len(lines)):
    if "certain_phrase" in lines[i]:
        break
    else:
        print(line,end='')
for num in range(38):
    del lines[i]

Answer 4

with open('temp.txt','r') as fin:
    for line in fin:
        print(line,end="") #you want to print the phrase, right?
        if "certain_phrase" in line:
            for _ in range(38):
                next(line)

在Python中无法识别循环变量

4 个答案: