using *args and **kwargs as a substitute for function's arguments

Question

I hava a question about *args and **kwargs. I know that they are used when you do not know how many arguments will be passed to function. But can it be a substitute for some arguments that are actually required when I do not know what those are?

If there is a function:

def functionName(a, b):
    ...some code...
    doSomethingUsing(a)
    doSomethingUsing(b)

If I do not what arguments does the function take can I simply use functionName(*args, **kwargs) - or functionName(*args)? I noticed that some people tend to use it that way - but I am not sure if this is how * and ** work in python?

Answer 1

Calling function(*args) is equivalent to function(arg[0], arg[1],...,arg[N]).

If you don't know what arguments the function is expecting, just call it and look at the exception:

>>> def f(a,b,c):
...     pass
...
>>> f()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: f() missing 3 required positional arguments: 'a', 'b', and 'c'

Or you could use the interactive help.

>>> help(f)
Help on function f in module __main__:

f(a, b, c)