请将下列shell语句转换为python语句：while true; do [ -z "${1:-}" ] && break; case "$1" in --help|-h) if [ -z "$help_message" ]; then echo "No help found." 1>&2; else printf "$help_message\n" 1>&2 ; fi; exit 0 ;; --*=*) echo "$0: options to scripts must be of the form --name value, got '$1'" exit 1 ;; --*) name=`echo "$1" | sed s/^--// | sed s/-/_/g`; eval '[ -z "${'$name'+xxx}" ]' && echo "$0: invalid option $1" 1>&2 && exit 1; oldval="`eval echo \\$$name`"; if [ "$oldval" == "true" ] || [ "$oldval" == "false" ]; then was_bool=true; else was_bool=false; fi eval $name=\"$2\"; if $was_bool && [[ "$2" != "true" && "$2" != "false" ]]; then echo "$0: expected \"true\" or \"false\": $1 $2" 1>&2 exit 1; fi shift 2; ;; *) break; esac done

以下是将shell语句转换成Python语句的示例代码：

import sys
import re

while True:
    if len(sys.argv) < 2:
        break
    arg = sys.argv[1]
    if arg in ["--help", "-h"]:
        if help_message is None:
            print("No help found.", file=sys.stderr)
        else:
            print(help_message, file=sys.stderr)
        sys.exit(0)
    elif re.match(r'--\*=.*', arg):
        print(f"{sys.argv[0]}: options to scripts must be of the form --name value, got '{arg}'", file=sys.stderr)
        sys.exit(1)
    elif re.match(r'--.*', arg):
        name = arg[2:].replace("-", "_")
        if name not in globals():
            print(f"{sys.argv[0]}: invalid option {arg}", file=sys.stderr)
            sys.exit(1)
        oldval = globals()[name]
        was_bool = isinstance(oldval, bool)
        if was_bool and arg == "--" + name and len(sys.argv) > 2 and sys.argv[2] in ["true", "false"]:
            val = sys.argv[2] == "true"
            del sys.argv[2]
            sys.argv[1] = "--" + name
        elif was_bool and arg == "--" + name:
            val = not oldval
        elif len(sys.argv) > 2:
            val = sys.argv[2]
            del sys.argv[2]
            sys.argv[1] = "--" + name
        else:
            print(f"{sys.argv[0]}: expected value after {arg}", file=sys.stderr)
            sys.exit(1)
        if was_bool and not isinstance(val, bool):
            print(f"{sys.argv[0]}: expected 'true' or 'false': {arg} {val}", file=sys.stderr)
            sys.exit(1)
        globals()[name] = val
    else:
        break

请注意，在Python中，变量名不能包含连字符，因此我们将所有连字符替换为下划线。另外，我们使用Python的内置正则表达式模块`re`来匹配参数。

此代码假定您已经将命令行参数传递给脚本，并且在Python中，您可以使用全局`globals()`函数来访问全局变量。