*args and **kwargs

PythonBy AI.CruzUpdated 31 August 2026

Collecting however many arguments a caller passes, and unpacking a list or dict back into a call.

Overview

Collecting

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

total(1, 2, 3) gives args = (1, 2, 3). total() gives args = (). The function accepts any number of positional arguments without knowing in advance how many, and inside it args is an ordinary tuple.

Two stars do the same for keyword arguments:

def describe(**kwargs):

describe(name="ana", score=91) gives kwargs = {"name": "ana", "score": 91} — an ordinary dict.

The names are pure convention. *items and **options work identically; the stars carry the meaning. Convention is strong enough here that using different names in a general-purpose helper will raise eyebrows, but in a specific function a descriptive name often reads better.

args_kwargs.py

def total(*args):
    print("  args is a tuple:", args)
    return sum(args)

print(total(1, 2, 3))
print(total(5))
print(total())

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

describe(name="ana", score=91)

# Both together, in the required order.
def report(label, *values, **options):
    print(f"{label}: {values}  options={options}")

report("scores", 91, 78, 85, sort=True, limit=2)

unpacking_calls.py

# The same star, used at the call site, does the opposite:
# it spreads a collection back out into arguments.
def volume(length, width, height):
    return length * width * height

dims = [2, 3, 4]
print("without star:", end=" ")
try:
    print(volume(dims))
except TypeError as e:
    print("TypeError:", e)

print("with star   :", volume(*dims))

settings = {"length": 2, "width": 3, "height": 4}
print("with **     :", volume(**settings))

# Very common use: pass everything straight through to another function.
def logged(func, *args, **kwargs):
    print(f"  calling {func.__name__} with {args} {kwargs}")
    return func(*args, **kwargs)

print("result      :", logged(volume, 2, 3, height=4))

# Unpacking works for building collections too.
a = [1, 2]
b = [3, 4]
print("merged list :", [*a, *b])
print("merged dict :", {**{"x": 1}, **{"y": 2}})

Worth knowing

*args collects extra positional arguments into a tuple; **kwargs collects extra keyword ones into a dict.

The names are convention, not syntax. The stars are the syntax.

Order in a definition: normal, then *args, then **kwargs.

At a call site the stars do the reverse - they spread a list or dict back into arguments.

*args and **kwargs

Overview

Collecting

args_kwargs.py

unpacking_calls.py

Worth knowing

Check yourself

*args and **kwargs

About the author

*args and **kwargs

Overview

Collecting

args_kwargs.py

unpacking_calls.py

Worth knowing

Check yourself

*args and **kwargs

More in Python

About the author