How to split a string into command line arguments like the shell in python?

Question

I have command line arguments in a string and I need to split it to feed to argparse.ArgumentParser.parse_args.

I see that the documentation uses

Answer 1

If you're parsing a windows-style command line, then shlex.split doesn't work correctly - calling subprocess functions on the result will not have the same behavior as passing the string directly to the shell.

In that case, the most reliable way to split a string like the command-line arguments to python is... to pass command line arguments to python:

import sys
import subprocess
import shlex
import json  # json is an easy way to send arbitrary ascii-safe lists of strings out of python

def shell_split(cmd):
    """
    Like `shlex.split`, but uses the Windows splitting syntax when run on Windows.

    On windows, this is the inverse of subprocess.list2cmdline
    """
    if os.name == 'posix':
        return shlex.split(cmd)
    else:
        # TODO: write a version of this that doesn't invoke a subprocess
        if not cmd:
            return []
        full_cmd = '{} {}'.format(
            subprocess.list2cmdline([
                sys.executable, '-c',
                'import sys, json; print(json.dumps(sys.argv[1:]))'
            ]), cmd
        )
        ret = subprocess.check_output(full_cmd).decode()
        return json.loads(ret)

One example of how these differ:

# windows does not treat all backslashes as escapes
>>> shell_split(r'C:\Users\me\some_file.txt "file with spaces"', 'file with spaces')
['C:\\Users\\me\\some_file.txt', 'file with spaces']

# posix does
>>> shlex.split(r'C:\Users\me\some_file.txt "file with spaces"')
['C:Usersmesome_file.txt', 'file with spaces']

# non-posix does not mean Windows - this produces extra quotes
>>> shlex.split(r'C:\Users\me\some_file.txt "file with spaces"', posix=False)
['C:\\Users\\me\\some_file.txt', '"file with spaces"']