*args and **kwargs in Python

Why args and kwargs

Sometimes you do not know in advance how many arguments a function will get. *args and **kwargs let a function accept any number of arguments. *args gathers extra positional values, and **kwargs gathers extra named values.

*args — many positional values

def add(*args):
    total = 0
    for n in args:
        total += n
    return total

print(add(1, 2, 3))       # 6
print(add(5, 10, 15, 20)) # 50

The *args collects however many numbers you pass into a tuple, so the same function works for 3 numbers or 4 — or any count.

**kwargs — many keyword values

def info(**kwargs):
    for key, value in kwargs.items():
        print(key, "=", value)

info(name="Aman", age=18, city="Delhi")

**kwargs collects named arguments into a dictionary. You can loop its .items() to read each key and value.

Using both together

def demo(a, *args, **kwargs):
    print("a:", a)
    print("args:", args)
    print("kwargs:", kwargs)

demo(1, 2, 3, x=10, y=20)

The regular parameter a takes the first value, *args catches the rest of the positional ones, and **kwargs catches the named ones. Order matters: normal, then *args, then **kwargs.

Unpacking with * and **

The same symbols can spread a list or dict back into arguments when calling.

def add(a, b, c):
    return a + b + c

nums = [1, 2, 3]
print(add(*nums))               # spreads list -> add(1,2,3)

data = {"a": 1, "b": 2, "c": 3}
print(add(**data))              # spreads dict -> add(a=1,b=2,c=3)

Here * and ** do the reverse of collecting — they unpack a list into positional arguments and a dict into keyword arguments.

Common mistakes

• Wrong parameter order. It must be normal params, then *args, then **kwargs.
• Thinking the names are required. Only * and ** matter; the names are convention.
• Mixing up the types. args is a tuple, kwargs is a dict — access them accordingly.
• Forgetting to unpack. Passing a whole list where separate values are needed — use *list.

Summary

• *args lets a function take any number of positional values (as a tuple).
• **kwargs lets it take any number of named values (as a dict).
• Order: normal parameters, then *args, then **kwargs.
• Only * and ** matter — the names are convention.
• Use * and ** when calling to unpack a list or dict.

Next, review the basics in Python functions, or explore list comprehension.