仅当以下行未注释时才提取注释行答案

【问题标题】：extract the commented lines only if the following line is not commented仅当以下行未注释时才提取注释行
【发布时间】：2021-07-28 08:50:27
【问题描述】：

我有一个文件如下：

cat file.txt

# unimportant comment
# unimportant comment
# unimportant comment
# important line
blah blah blah
blah blah blah
# insignificant comment
# significant comment
xyz
xyz

我想打印以'#' 开头的行，前提是以下行没有被注释。

我希望提取以下两行：

# important line
# significant comment

我尝试了以下方法，但它不起作用：

with open("file.txt","r") as fp:
    for line in fp:
        if line[0] == '#':
            pos = fp.tell()
            previous_line_comment = True
        elif line[0] != '#' and previous_line_comment:
            fp.seek(pos)
            print(fp.readline())
            previous_line_commented = False
        else:
            fp.readline()

【问题讨论】：

标签： python seek

【解决方案1】：

让我们在迭代时存储每条评论的值，然后在遇到不是评论的行时输出上一行。

with open('test.txt', 'r') as file:
    ## Set previous comment to None, we will store the comment in here
    previous_comment = None
    for line in file.readlines():
        ## We use startswith to return a boolean T/F if the string starts with '#'
        line_is_comment = line.startswith('#')
        
        if line_is_comment:
            ## If the current line is a comment, set the previous comment to the current line
            previous_comment = line
            continue
        elif previous_comment and not line_is_comment:
            ## If previous comment exists, and the current line is not a comment -> output
            print(previous_comment)
            previous_comment = None
        else:
            previous_comment = None

输出

# important line

# significant comment

【讨论】：

【解决方案2】：

& 是按位与运算符。我相信您打算使用的是逻辑 AND。

elif line[0] != '#' and previous_line_comment:

【讨论】：

刚刚修复了这个问题。但它不会修复代码