Default arguments with *args and **kwargs

Question

In Python 2.x (I use 2.7), which is the proper way to use default arguments with *args and **kwargs?
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Answer 1

This answer is an extension of what Daniel Américo suggested.

This decorator assigns default kwarg values if they are not strictly defined.

from functools import wraps

def force_kwargs(**defaultKwargs):
    def decorator(f):
        @wraps(f)
        def g(*args, **kwargs):
            new_args = {}
            new_kwargs = defaultKwargs
            varnames = f.__code__.co_varnames
            new_kwargs.update(kwargs)
            for k, v in defaultKwargs.items():
                if k in varnames:
                    i = varnames.index(k)
                    new_args[(i, k)] = new_kwargs.pop(k)
            # Insert new_args into the correct position of the args.
            full_args = list(args)
            for i, k in sorted(new_args.keys()):
                if i <= len(full_args):
                    full_args.insert(i, new_args.pop((i, k)))
                else:
                    break
            # re-insert the value as a key-value pair
            for (i, k), val in new_args.items():
                new_kwargs[k] = val
            return f(*tuple(full_args), **new_kwargs)
        return g
    return decorator

Result

@force_kwargs(c=7)
def f(a, b='B', c='C', d='D', *args, **kw):
    return a, b, c, d, args, kw
#                               a    b  c    d  args      kwargs
f('r')                      # 'r', 'B', 7, 'D',   (),         {}
f(1,2,3)                    #   1,   2, 7,   3,   (),         {}
f(1, 2, 3, b=3, c=9, f='F') #   1,   3, 9,   2, (3,), {'f': 'F'}

Variant

If you want to use the default values as written in the function definition, you could access the argument default values using f.func_defaults, which lists the default values. You would have to zip them with the end of the f.__code__.varnames to match these default values with the variable names.