修改Python3 argparse辅助函数以兼容Python2，适配EMC Unity REST API工具

Hey there! Let's walk through this problem clearly, starting with understanding that argument helper function, then adapting it for Python 2, and finally getting your create_lun function integrated.

That little function is a clever shortcut to clean up argparse parameter definitions. Here's exactly how it works:

• The *name_or_flags parameter catches all positional inputs (like "-n", "--name" for a named flag pair) as a tuple.
• The **kwargs parameter grabs all keyword arguments you pass (like help="LUN display name", required=True, or type=int) into a dictionary.
• The function returns a tuple: the first element is a list of your flags/names, and the second is the config dictionary. This lets you easily unpack it when adding arguments to your parser with parser.add_argument(*args, **kwargs).

The only Python 3-specific part here is the [*name_or_flags] syntax—it uses Python 3's list unpacking, which isn't supported in Python 2. That's the key fix we need to make.

Since Python 2 doesn't allow * unpacking inside a literal list, we just need to convert the name_or_flags tuple to a list directly. Here's the updated, Python 2-compatible version:

def argument(*name_or_flags, **kwargs):
    # Convert the positional args tuple to a list (works in both Python 2 and 3)
    return (list(name_or_flags), kwargs)

This behaves exactly like the original Python 3 function, but will run without syntax errors in Python 2.7+ (which has argparse in the standard library, so you're good there).

Now let's get this set up to handle your LUN creation command. Here's a step-by-step example:

1. Define your command-line arguments using the adapted argument function:

# Define arguments for the create-lun command
create_lun_args = [
    argument("-n", "--name", help="Name of the LUN to create", required=True),
    argument("-s", "--size", type=int, help="Size of the LUN in gigabytes", required=True),
    argument("-p", "--pool-id", help="ID of the storage pool to allocate from", required=True),
    # Add any other args your API needs (like thin provisioning, description, etc.)
]

2. Set up your argparse parser with subcommands, and attach the create_lun arguments:

from __future__ import print_function  # Makes print() work like Python 3 (optional but helpful)
import argparse

def main():
    parser = argparse.ArgumentParser(description="EMC Unity REST API Management Tool")
    subparsers = parser.add_subparsers(dest="command", help="Available commands")
    
    # Create the create-lun subcommand parser
    create_lun_parser = subparsers.add_parser("create-lun", help="Create a new LUN on EMC Unity")
    for arg_flags, arg_config in create_lun_args:
        create_lun_parser.add_argument(*arg_flags, **arg_config)
    
    # Parse incoming command-line arguments
    args = parser.parse_args()
    
    # Route to the correct function based on the command
    if args.command == "create-lun":
        create_lun(args.name, args.size, args.pool_id)

def create_lun(lun_name, size_gb, pool_id):
    # Replace this with your actual EMC Unity REST API logic
    # Example steps: authenticate to the API, build the LUN creation payload, send POST request
    print(f"Creating LUN '{lun_name}' with size {size_gb}GB in pool {pool_id}")
    # Add your API calls here (using urllib2 or requests library—note: requests works in Python 2.7 too)

3. Python 2-specific notes:
   • If you're using the requests library (recommended for API calls), make sure you install a Python 2-compatible version (like requests==2.27.1).
   • Handle Unicode strings carefully—convert API responses to UTF-8 if needed to avoid encoding errors.

内容的提问来源于stack exchange，提问作者totallyGreg