Using positional arguments from argparse as function name

问题

I have set up a script with argparse that gives me the following NameSpace:

Namespace(action='list', input='all', target='domain')

I have made a few functions which are called according to the positionals, and at the moment I have a working situation by calling them with blurbs of code like this one:

if args.action == 'list':
    if len(sys.argv) == 2:
        parser.print_help()
        sys.exit(0)
elif args.target == 'domain':
    domain_list()
elif args.target == 'forwarding':
    forwarding_list()
elif args.target == 'transport':
    transport_list()
elif args.target == 'user':
    user_list()
else:
    all_list()

I know this can be done way, way better than this; but with my limited knowledge of Python, I can't seem to figure this one out.

Recap: I want something like, if at all possible (pseudocode)

if args.action == 'add':
    target = args.target
    target_add()

where target_add() is something like domain_add().

Thanks in advance!

回答1:

It sounds like action could be list or add, while target could be domain, forwarding, transport, or user. Yes, you would end up with a lot of if..then..else code if you had to manually list what each combination of options would do.

Here is a way to simplify this:

Use itertools.product to generate all the possible combinations of options.
Use a whitelist dispatch dict to map options to functions. The keys are 2-tuples, such as ('domain','list'), or ('transport','add'). The values are the associated function objects.

import itertools as IT

targets = 'domain forwarding transport user'.split()
actions = 'list add'.split()

dispatch = {key:globals()['%s_%s' % key] for key in IT.product(targets, actions)}

# This calls the function specified by (target, action).
# The `dict.get` method is used so that if the key is not in `dispatch`, the `all_list` function is called.
dispatch.get((args.target, args.action), all_list)()

来源：https://stackoverflow.com/questions/14101989/using-positional-arguments-from-argparse-as-function-name

标签

python

argparse