这个脚本的 re.search() 中的正则表达式有什么作用？

Question

I hope someone could help me with this code, I am looking forward to use it.

# Absolute path of the script:
ROOT_DIR = os.path.dirname(os.path.abspath(__file__))

# Real path of the script:
REAL_DIR = re.search(r'(?<=\[)(.*?)(?=\])', 
                     subprocess.check_output('dir {} /al | findstr "<JUNCTION>" | findstr Ducati'.format(ROOT_DIR.replace("Ducati", "")), stderr=subprocess.STDOUT, shell=True).decode('ASCII')).group()

# Absolute path of the sandbox
SANDBOX_DIR = os.path.abspath(os.path.join(REAL_DIR, '..', '..'))

# Simple FlashTool Path
FLASHTOOL_DIR = os.path.abspath(
    os.path.join(SANDBOX_DIR, 'DevelopmentEnvironmentPlatformTools', 'Tool.UDSFlashtool',
                'build', 'INSTALL', 'flashtool', 'bin', 'simple-flashtool.exe'))

# Network config file
CONF_DIR_PATH = os.path.abspath(os.path.join(FLASHTOOL_DIR, '..', '..', 'conf'))

# Log file path
LOG_ROOT_PATH = os.path.join(os.path.dirname(os.path.dirname(os.path.dirname(ROOT_DIR))), 'tta_logs', 'FlashTool')

Especially this part

# Real path of the script:
REAL_DIR = re.search(r'(?<=\[)(.*?)(?=\])', 
                     subprocess.check_output('dir {} /al | findstr "<JUNCTION>" | findstr Ducati'.format(ROOT_DIR.replace("Ducati", "")), stderr=subprocess.STDOUT, shell=True).decode('ASCII')).group()

Answer 1

If you're asking specifically what the regex re.search(r'(?<=\[)(.*?)(?=\])' does, it's finding strings that are surrounded by square braces and capturing the content inside the braces.

• (?<=\[) is a positive lookbehind, asserting that before this match, there's a square opening brace [
• (.*?) is a capture group that selects any characters any number of times, but the ? quantifier means it captures as few as possible. This means it won't usually capture the closing square brackets ahead of it; if you've got a[s]df[ghj]kl , it'll capture s and ghj instead of s]df[ghj .
• (?=\]) is a positive lookahead, asserting that after this match, there's a square closing brace ]

See it in action here!

I can sort of guess at the rest of the script, which looks like it's searching for symbolic links ("shortcuts") to something. The presence of dir {} /al makes me think this script is supposed to be run on Windows. subprocess.check_output() is going to run the command string inside of it, and then pipe its (possibly multiline) output to the regex, which is then going to use .group() to create a tuple of the matches it finds.