*args & **kwargs

*args — any number of positional arguments

*args collects every extra positional argument into a tuple.

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

total(1, 2, 3)       # 6
total(1, 2, 3, 4, 5) # 15

JS's equivalent is rest parameters:

function total(...numbers) {
  return numbers.reduce((a, b) => a + b, 0);
}

Same idea, different symbol — Python uses *, JS uses ....

**kwargs — any number of keyword arguments

**kwargs collects every extra name=value argument into a dict.

def create_user(**details):
    print(details)

create_user(name="John", age=25)
# {"name": "John", "age": 25}

The closest JS equivalent is just accepting an object:

function createUser(details) {
  console.log(details);
}

createUser({ name: 'John', age: 25 });

The difference: in Python the caller doesn't wrap anything in braces — **kwargs gathers up whatever named arguments were passed directly.

Naming is just convention

args and kwargs aren't keywords — only the * and ** matter. You could name them anything, but *args/**kwargs is the convention you'll see in almost all Python code.

Using them together

A function can accept regular parameters, *args, and **kwargs all at once — always in this order:

def example(a, b, *args, **kwargs):
    print(a, b, args, kwargs)

example(1, 2, 3, 4, x=5, y=6)
# 1 2 (3, 4) {'x': 5, 'y': 6}