如何从一个文件中删除行，直到一个特定的字符？[Python]

Question

我想写一个python脚本，通过扫描一个文件，直到找到一个给定的单词，然后从这个单词中删除文件中的所有行，直到找到下一个给定的单词，如图所示。

Line1
Line2
Line3
Key-Word
Line4
Line5
Key-Word2
Line6
Line7

结果是：

Line1
Line2
Line3
Key-Word2
Line6
Line7

到目前为止，我已经成功地让它检测到了关键词，但我不知道如何让它删除所有的行，然后从关键词2开始继续。

Answer 1

读取文件的行数，然后把它写回来，除了从开始键到停止键的行数，下面是一个例子。

def erase(file_name: str, start_key: str, stop_key: str):
    """
    This function will delete all line from the givin start_key
    until the stop_key. (include: start_key) (exclude: stop_key)
    """
    try: 
        # read the file lines
        with open(file_name, 'r+') as fr: 
            lines = fr.readlines()
        # write the file lines except the start_key until the stop_key
        with open(file_name, 'w+') as fw:
            # delete variable to control deletion
            delete = False
            # iterate over the file lines
            for line in lines:
                # check if the line is a start_key
                # set delete to True (start deleting)
                if line.strip('\n') == start_key:
                     delete = True
                # check if the line is a stop_key
                # set delete to False (stop deleting)
                elif line.strip('\n') == stop_key:
                     delete = False
                # write the line back based on delete value
                # if the delete setten to True this will
                # not be executed (the line will be skipped)
                if not delete: 
                    fw.write(line)
    except RuntimeError as ex: 
        print(f"erase error:\n\t{ex}")

使用方法：

erase('file.txt', 'Key-Word', 'Key-Word2')

file.txt (输入):

Line1
Line2
Line3
Key-Word
Line4
Line5
Key-Word2
Line6
Line7

在运行该函数后，

Line1
Line2
Line3
Key-Word2
Line6
Line7

Answer 2

理想情况下，你应该打开文件两次。一次是读取行，一次是写入。如果由于某种原因，你在你的forloop中试图同时进行读和写时出错，你可能会得到一个部分受影响的文件。

你需要小心地删除行间的空白，因为字符"\n "会被附加到你的字符串中。

keyword_found = False
with open("line_file.txt", "r") as f:
    lines = f.readlines()
with open("line_file.txt", "w") as f:
    while (lines):
        line = lines.pop(0).strip("\n")
        if line == 'you':
            keyword_found = True
        if line == 'friend':
            keyword_found = False
        if not keyword_found:
            f.write(line + "\n")