产生带有反斜杠但不包括注释块的连接行

Question

当前正在尝试创建一个生成器函数，该函数一次生成一行文件，同时忽略注释块并将末尾带有反斜杠的行连接到下一行。因此，对于这段文字：

# this entire line is a comment - don't include it in the output
<line0>
# this entire line is a comment - don't include it in the output
<line1># comment
<line2>
# this entire line is a comment - don't include it in the output
<line3.1 \
line3.2 \
line3.3>
<line4.1 \
line4.2>
<line5># comment \
# more comment1 \
more comment2>
<line6>
# here's a comment line continued to the next line \
this line is part of the comment from the previous line

理想的输出是：

<line0>
<line1>
<line2>
<line3.1 line3.2 line3.3>
<line4.1 line4.2>
<line5>
<line6>

以下是我目前掌握的代码：

try:
    file_name = open('path/to/file.txt', 'r')
except FileNotFoundError:
    print("File could not be found. Please check spelling of file name!")
    sys.exit()

#Read lines in file
Lines = file_name.read().splitlines()

class FileLineGen:
    def get_filelines(path: str) -> Iterator[str]:
        for line in Lines:
            #Exclude a line if it starts with #
            if line.startswith("#"):
                line.replace(line, "")
                continue
            if "#" in line:
                #Split at where the # is located
                line.split('#')
                #Yield everything before the comment block
                yield line.split('#')[0]
                continue
            if line.endswith('\\'):
                #Yield everything but the backslash
                line = line[:-1]
                yield line
                continue
            #Yield the line in all other cases
            else:
                yield line

    gen = get_filelines(file_name)
    for line in Lines:
        print(next(gen))

这将产生以下输出：

<line0>
<line1>
<line2>
<line3.1 
line3.2 
line3.3>
<line4.1 
line4.2>
<line5>
more comment2>
<line6>
this line is part of the comment from the previous line

因此，我已经能够删除反斜杠，但我尝试了连接的变化，但没有任何效果。理想的逻辑是首先将反斜杠与下一行连接起来，这样，如果行的开头有一个#，那么该行将被自动排除（并且后面的注释不会包含在输出中）

编辑： 在FileLineGen类中使用with block打开文件的新输出：

    with open('/path/to/file.txt') as f:
        for line in my_generator(f):
            print(line)

<line0>

<line1>
<line2>

<line3.1 line3.2 line3.3>

<line4.1 line4.2>

<line5>
<line6>

Answer 1

您有两个运算符，#和\。后者优先于前者。这意味着您应该先检查并处理它。以下是使用列表作为缓冲区来建立行的一种简单方法：

def my_generator(f):
    buffer = []
    for line in f:
        line = line.rstrip('\n')
        if line.endswith('\\'):
            buffer.append(line[:-1])
            continue
        line = ''.join(buffer) + line
        buffer = []
        if '#' in line:
            line = line[:line.index('#')]
        if line:
            yield line

包装一个iterable行并使用ducktyping的好处是，您可以传入任何行为类似于字符串容器的内容，而不仅仅是文本文件：

text = """# this entire line is a comment - don't include it in the output
<line0>
# this entire line is a comment - don't include it in the output
<line1># comment
<line2>
# this entire line is a comment - don't include it in the output
<line3.1 \
line3.2 \
line3.3>
<line4.1 \
line4.2>
<line5># comment \
# more comment1 \
more comment2>
<line6>
# here's a comment line continued to the next line \
this line is part of the comment from the previous line'"""

for line in my_generator(text.splitlines()):
    print(line)

结果如预期：

<line0>
<line1>
<line2>
<line3.1 line3.2 line3.3>
<line4.1 line4.2>
<line5>
<line6>

编写循环的另一种方法是

print('\n'.join(my_generator(text.splitlines())))

Answer 2

我建议使用re.sub方法

def line_gen(text: str):

    text = re.sub(r"\s+\\\n", '', text)   # Remove any \ break
    text = re.sub(r"#(.*)\n", '\n', text) # Remove any comment
    # If the last line it is a comment it won't have a final \n.
    # We have to remove it as well.
    text = re.sub(r"#.*", '', text) 

    for line in text.rsplit():  # Using rsplit here we get ride of all unwanted spaces.
        yield line


with open("/tmp/data.txt") as f:
    text = f.read()

    for line in line_gen(text):
        print(line)

data.txt的内容

# this entire line is a comment - don't include it in the output
<line0>
# this entire line is a comment - don't include it in the output
<line1># comment
<line2>
# this entire line is a comment - don't include it in the output
<line3.1 \
line3.2 \
line3.3>
<line4.1 \
line4.2>
<line5># comment \
# more comment1 \
more comment2>
<line6>
# here's a comment line continued to the next line \
this line is part of the comment from the previous line

结果：

<line0>
<line1>
<line2>
<line3.1line3.2line3.3>
<line4.1line4.2>
<line5>
<line6>