如何从匹配字符串中删除多行文本？

Question

I have the following snippet I would like to completely remove with a regex (or some other method).

# ---------------------------------------------------------------------------------------------------------------------
# MODULE PARAMETERS
# These are the variables we have to pass in to use the module specified in the terragrunt configuration above
# ---------------------------------------------------------------------------------------------------------------------

Is there syntax to tell the match to get rid of everything between the two matches?

It seems like it should be easy to do, but for some reason I have only been able to find a regex that pulls the first and last match out via this code. I have tried a number of permutations of this regex but can't get it working.

...
re.sub(r'# --*[\S\s]*---', '', lines[line])
...

This regex tool says that my regex should work.

EDIT:

The text I am interested in matching is being read in one line at a time.

...
for the_file in files_to_update:
    with open(the_file + "/the_file", "r") as in_file:
        lines = in_file.readlines()

And subsequently being iterated over. The snippet above is acutally happening in this loop.

for line in range(len(lines)):

Answer 1

You should read in the file into a single variable to be able to run a regex on it, that can match more than one line of text.

You may use

with open(filepath, 'r') as fr:
  with open(filesavepath, 'w') as fw:
    fw.write( re.sub(r'^# -+(?:\n# .*)*\n# -+$\n?', '', fr.read(), flags=re.M) )

See the Python demo and a regex demo .

Here, fr is the handle of the file you read from, and fw is the handle of the file you are writing to. The input for re.sub is fr.read() , this method grabs the whole file contents and passes to the regex engine.

The regex means:

• ^ - start of a line (due to re.M )
• # -+ - a # , space and then one or more hyphens
• (?:\n#.*)* - 0 or more repetitions of a newline, # , space, any text up to the end of a line
• \n - a newline
• # -+$ - # , space, one or more hyphens and end of a line
• \n? - an optional newline.

A non-regex way of removing the comments is by reading line by line, checking if a line starts with # --- and set a flag that would enable checking if we are inside the comment or not:

for line in fr:
    if line.startswith('# ---'):
        flag = not flag
        continue
    if flag:
        lines.append(line)
        
print("\n".join(lines))

See this Python demo .

Answer 2

Why not just use string functions with a small function?

data = """
# ---------------------------------------------------------------------------------------------------------------------
# MODULE PARAMETERS
# These are the variables we have to pass in to use the module specified in the terragrunt configuration above
# ---------------------------------------------------------------------------------------------------------------------

foo
# some other comment
bar

"""

def remover(block):
    remove = False

    for line in block.split("\n"):
        if line.startswith("# ---"):
            remove = not remove
        elif not remove:
            yield line

cleaned = [line for line in remover(data)]
print(cleaned)

This yields

['', '', 'foo', '# some other comment', 'bar', '', '']