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name

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name Punditsdkoslkdosdkoskdo

How to pass on argparse argument to function as kwargs?

I have a class defined as follows

class M(object):
    def __init__(self, **kwargs):
        ...do_something

and I have the result of argparse.parse_args(), for example:

> args = parse_args()
> print args
Namespace(value=5, message='test', message_type='email', extra="blah", param="whatever")

I want to pass on the values of this namespace (except message_type) to create an instance of the class M. I have tried

M(args)

but got an error

TypeError: __init__() takes exactly 1 argument (2 given)

which I do not understand. How can I

  1. remove the value message_type from the list in args
  2. pass on the values as if I would type M(value=5, message='test', extra="blah", param="whatever") directly.

You need to pass in the result of vars(args) instead:

M(**vars(args))

The vars() function returns the namespace of the Namespace instance (its __dict__ attribute) as a dictionary.

Inside M.__init__(), simply ignore the message_type key.

  • 44
Reply Report
      • 1
    • Thats exactly what I need. Thanks. Except for removal of the certain key. I need it to be removed, I cannot just ignore it for reasons outside the scope of this question.
    • I suggest to do arg_dict = dict((k,v) for k,v in vars(args).items() if k!="message_type") to avoid possible undefined behaviour with vars.
      • 1
    • @Alex: what undefined behaviour with vars? You can filter out the message_type key that way, sure, but do that for it's own sake, not because vars() might have undefined behaviour (which it doesn't).
      • 2
    • @Alex: I'd rather make the M class more robust in the face of extra keyword arguments it doesn't support.
      • 2
    • @Alex: The values are copied into the M.__init__ parameters, so the original mapping is never modified. If you need to regulate what keywords are passed in, use a whitelist instead.

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