What Do *args and **kwargs Mean?

A parameter with a single star in front of it collects any extra positional arguments into a tuple. A parameter with a double star in front of it collects any extra keyword arguments into a dictionary.

def collect(*args, **kwargs):
    print('args:', args, type(args).__name__)
    print('kwargs:', kwargs, type(kwargs).__name__)
    print('first arg:', args[0] if args else None)
    print('key:', kwargs.get('key'))


collect(1, 2, 3, key='value', other=42)

The output shows the arguments as the tuple (1, 2, 3) and the keyword arguments as a dictionary with the key and other keys inside it. The types matter as much as the values here. The extra positional arguments arrive as a tuple because positional arguments are ordered, and the extra keyword arguments arrive as a dictionary because keyword arguments are named.

There are two rules about the order of the parameters. The *args and **kwargs parameters must come last in the signature, after any ordinary parameters. But a bare * can also be used on its own, and that is the cleanest way to mark the parameters after it as keyword-only, so that a caller cannot pass one positionally by mistake.

The same syntax is used in the other direction when you call a function. A single star unpacks an iterable into positional arguments, and a double star unpacks a dictionary into keyword arguments.

collect(*[1, 2, 3], **{'key': 'value', 'other': 42})

That call is exactly the same as the literal call above it. The practical use of this is forwarding, where a wrapper function accepts *args and **kwargs and passes them straight through to another function. That is how decorators and framework hooks are usually written.

*args collects extra positional arguments into a tuple, and **kwargs collects extra keyword arguments into a dictionary. Together they are the mechanism Python gives you for a function whose signature you cannot fully predict, which happens more often than it first appears.

Use *args when the number of positional arguments varies and each one matters, such as a function that averages any number of values or forwards a call to another API. Use **kwargs when you want to accept named options that you do not want to spell out in the signature, such as a configuration helper that passes extra options through to a lower-level library.

The most valuable real-world use is forwarding. A wrapper that takes *args and **kwargs and passes them on unchanged can adapt any function without knowing its signature. That is the basis of decorators, of retry wrappers, of timing helpers, and of most framework middleware. It is why you see the pattern even in code that does not really need a variable number of arguments.

There are two cautions. First, *args and **kwargs hide the signature from anyone reading the code and from type checkers, so a function with a fixed and short parameter list is much better documentation. Second, a **kwargs dictionary lets a caller pass a misspelled keyword, and if the function ignores unknown keys the misspelling is accepted quietly. That is a common source of bugs where an option simply does nothing.

A good middle ground for an interview answer is to use a bare * to force keyword-only arguments for the options that really matter, and to keep **kwargs only for pass-through extras. That keeps the important parameters visible while still allowing some flexibility.