Functions, kwargs, *args & Defaults

Keyword arguments, default values, and accepting any number of inputs

You've learned to define functions with parameters. Now let's make them smarter and more flexible, with default values, keyword arguments, and variable-length inputs.

Default parameters, optional arguments with fallback values
Give a parameter a default value using = in the function definition:

Default parameter valuespython

def greet(name, greeting="Hello"):
    print(f"{greeting}, {name}!")

greet("Alice")            # Hello, Alice!   (uses default)
greet("Bob", "Hi")        # Hi, Bob!        (overrides default)
greet("Carol", greeting="Hey")  # Hey, Carol!

Rule: Parameters with defaults must come AFTER parameters without defaults. def f(a=1, b) is a SyntaxError.

Keyword arguments, call by name, not position
You can pass arguments in any order if you name them:

Keyword argumentspython

def make_coffee(size, strength, milk=False):
    print(f"{size} {strength} coffee, milk: {milk}")

# Positional (order matters)
make_coffee("large", "strong")

# Keyword (order doesn't matter)
make_coffee(strength="mild", size="small", milk=True)

🤔Quick Check

Given def power(base, exp=2), which call returns 8?

*args, accept any number of positional arguments
The *args syntax packs all extra positional arguments into a tuple:

*args for variable argumentspython

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

print(add_all(1, 2, 3))        # 6
print(add_all(10, 20, 30, 40)) # 100

**kwargs, accept any number of keyword arguments
The **kwargs syntax packs extra keyword arguments into a dictionary:

**kwargs for named argumentspython

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

describe(name="Alice", age=30, city="London")
# name: Alice
# age: 30
# city: London

🤔Quick Check

Inside a function defined as def f(*args), what type is args?

Practice Exercises

0/3 solved

Exercise 1 of 3easyGuided

⏱ 00:00

Flexible Greeter

Write a function greet(name, title="", punctuation="!") that prints a greeting.
- greet("Alice") → Hello, Alice!- greet("Smith", title="Dr.", punctuation=".") → Hello, Dr. Smith.

solution.py

1 / 3

Exercise 2 of 3easy

⏱ 00:00

Sum Any Numbers

Write a function total(*nums) that returns the sum of any number of arguments.
- print(total(1, 2, 3)) → 6- print(total(10, 20)) → 30

solution.py

2 / 3

Exercise 3 of 3medium

⏱ 00:00

Profile Builder

Write a function build_profile(name, **info) that prints a profile card.
Call: build_profile("Alice", age=30, city="London", job="Engineer")
Expected output:Profile: Aliceage: 30city: Londonjob: Engineer

solution.py

3 / 3

Solve all 3 exercises to unlock completion

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