从文件python中删除字符串和字符串之前的所有行 [英] remove string and all lines before string from file python

问题描述

我有一个文件名，其中包含数千行数据. 我正在读取文件名并对其进行编辑.

I have a filename with thousands of lines of data in it. I am reading in the filename and editing it.

以下标记大约等于或大于900行(随文件而异):

The following tag is about ~900 lines in or more (it varies per file):

<Report name="test" xmlns:cm="http://www.domain.org/cm">

我需要在几个文件中删除该行及其之前的所有内容. 所以我需要代码来搜索该标签并删除它以及它上面的所有内容 它不会总是向下900行，它会有所不同；但是，标记将始终相同.

I need to remove that line and everything before it in several files. so I need to the code to search for that tag and delete it and everything above it it will not always be 900 lines down, it will vary; however, the tag will always be the same.

我已经有了读取行并写入文件的代码.我只需要找到该行并删除它以及它之前的所有内容的逻辑即可.

I already have the code to read in the lines and write to a file. I just need the logic behind finding that line and removing it and everything before it.

我尝试逐行读取文件，然后在命中该字符串后将其写入新文件，但是逻辑不正确:

I tried reading the file in line by line and then writing to a new file once it hits on that string, but the logic is incorrect:

readFile = open(firstFile)
lines = readFile.readlines()
readFile.close()
w = open('test','w')
for item in lines:
    if (item == "<Report name="test" xmlns:cm="http://www.domain.org/cm">"):
        w.writelines(item)
w.close()

此外，每个文件中的确切字符串都不相同.值"test"将有所不同.我也许需要检查标签名称"

任何帮助将不胜感激.

In addition, the exact string will not be the same in each file. The value "test" will be different. I perhaps need to check for the tag name ""

Any help will be much appreciated.

推荐答案

您可以使用tag_found这样的标志来检查何时将行写入输出.您最初将标志设置为False，然后在找到正确的标记后将其更改为True.当标志为True时，将行复制到输出文件.

You can use a flag like tag_found to check when lines should be written to the output. You initially set the flag to False, and then change it to True once you've found the right tag. When the flag is True, you copy the line to the output file.

TAG = '<Report name="test" xmlns:cm="http://www.domain.org/cm">'

tag_found = False
with open('tag_input.txt') as in_file:
    with open('tag_output.txt', 'w') as out_file:
        for line in in_file:
            if not tag_found:
                if line.strip() == TAG:
                    tag_found = True
            else:
                out_file.write(line)

PS:with open(filename) as in_file:语法正在使用Python所谓的上下文管理器"-请参见

PS: The with open(filename) as in_file: syntax is using what Python calls a "context manager"- see here for an overview. The short explanation of them is that they automatically take care of closing the file safely for you when the with: block is finished, so you don't have to remember to put in my_file.close() statements.

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