Unpacking more than one list as argument for a function

Question

If I have a function like:

def f(a,b,c,d):
    print a,b,c,d

Then why does this works:

f(1,2,3,4)
f(*[1,2,3,4])

But not this:

f(*[1,2] , *[3,4])
    f(*[1,2] , *[3,4])
               ^
SyntaxError: invalid syntax

?

EDIT : For information, the original problem was to replace one of the argument in a function wrapper. I wanted to replace a given member of the inputted *args and tried something like:

def vectorize_pos(f,n=0):
    '''
    Decorator, vectorize the processing of the nth argument
    :param f: function that dont accept a list as nth argument
    '''
    def vectorizedFunction(*args,**kwargs):
        if isinstance(args[n],list):
            return map(lambda x : f( *(args[:n]) , x , *(args[n+1,:]), **kwargs),args[n])
        else:
            return f(*args,**kwargs)
    return vectorizedFunction

That's where the question arose from. And I know there is other way do do the same thing but only wanted to understand why unpacking one sequence worked but not for more.

Answer 1

Because, as per the Function call syntax, this is how the argument list is defined

argument_list ::=  positional_arguments ["," keyword_arguments]
                     ["," "*" expression] ["," keyword_arguments]
                     ["," "**" expression]
                   | keyword_arguments ["," "*" expression]
                     ["," keyword_arguments] ["," "**" expression]
                   | "*" expression ["," keyword_arguments] ["," "**" expression]
                   | "**" expression

So, you can pass only one * expression per function call.