In method call args, how to override keyword argument of unpacked dict?

You can use the built-in dict type for that purpose. It accepts another dict as argument and additional key-value pairs as keyword arguments (which have precedence over the values in the other dict).

Thus you can create an updated dictionary via dict(template_vars, a=1).

You can unfold this dict as keyword arguments: func(**dict(...)).

Like that there is no need to change the signature of your function and you can update/add as many key-value pairs as you want.

You can do it in one line like this:

func(**{**mymod.template_kvps, 'a': 3})

But this might not be obvious at first glance, but is as obvious as what you were doing before.

What I would suggest is having multiple templates (e.g. template_kvps_without_a), but this would depend on your specific use case:

func(**mymod.template_kvps_without_a, a=3)

I'd consider function decorators as this keeps the syntax mostly the same as you requested. The implementation would look something like:

def combine(func):
  def wrapper(*args, **kwargs):
    fargs = {}
    if args and isinstance( args[0], dict ):
      fargs = args[0].copy()
    fargs.update(kwargs)
    return func(**fargs)
  return wrapper


@combine
def funky(**kwargs):
  for k,v in kwargs.iteritems():
    print "%s: %s" % (k, v)

# All of these work as expected
funky( {'a': 1, 'b': 2}, a=3 )
funky( {'a': 1, 'b': 2} )
funky( a=3 )