python中去掉文件的注释

import sys

import re

PY_PATTERN = re.compile(

    r"""

     \s*\#(?:[^\r\n])*

     | \s*__(?:[^\r\n]*)

     | "{3}(?:\\.|[^\\])*"{3}

     | '{3}(?:\\.|[^\\])*'{3}

     """,

    re.VERBOSE | re.MULTILINE | re.DOTALL

)

txt = open("cmd.txt").readlines()

b = re.sub(PY_PATTERN,'', ''.join(txt))

single = re.compile(r"\n\n")

b = re.sub(single,'\n',b)

print(b)