What do *args and **kwargs mean in Python?

The short version

In a function definition, *args gathers any extra positional arguments into a tuple, and **kwargs gathers any extra keyword arguments into a dictionary. The names are just convention; the stars do the work. At a call site, the same * and ** unpack a sequence or dictionary back into separate arguments.

Collecting arguments

def total(*args):
    return sum(args)

print(total(1, 2, 3))   # 6, args is (1, 2, 3)

args is an ordinary tuple, so you can loop over it or index it. This lets a function accept any number of positional values.

Collecting keyword arguments

def describe(**kwargs):
    for key, value in kwargs.items():
        print(f"{key} = {value}")

describe(colour="red", size="large")

kwargs is a normal dictionary, here {"colour": "red", "size": "large"}.

Using both together

The order is fixed: normal parameters, then *args, then **kwargs.

def log(label, *args, **kwargs):
    print(label, args, kwargs)

log("event", 1, 2, user="ana")   # event (1, 2) {'user': 'ana'}

Unpacking at the call site

The same stars work in reverse, spreading a collection into arguments. This is where the two ideas connect.

values = [1, 2, 3]
print(total(*values))   # same as total(1, 2, 3)

opts = {"colour": "red", "size": "large"}
describe(**opts)        # same as describe(colour="red", size="large")

Where this is genuinely useful

The common real use is a wrapper that passes arguments straight through to another function without needing to know them.

def timed(func, *args, **kwargs):
    # ... start a timer ...
    result = func(*args, **kwargs)
    # ... stop the timer ...
    return result

Here *args, **kwargs let timed forward whatever arguments the wrapped function expects, so one wrapper works for any function.

A caution

Do not reach for *args and **kwargs just to look flexible. Explicit named parameters document what a function accepts and let editors and type checkers help you. Use the star forms when the count really is variable or when you are genuinely forwarding arguments onward.