Default & keyword arguments

A parameter can have a default that is used when the caller leaves it out:

def brew(size="medium", sugar=0):
    return f"{size} coffee, {sugar} sugar"

brew()                    # medium coffee, 0 sugar
brew("large")             # large coffee, 0 sugar
brew(sugar=2)             # keyword argument: pick by name

Keyword arguments can come in any order.

See it run

def brew(size="medium", sugar=0):
    return f"{size}, {sugar} sugar"

a = brew()
b = brew("large")
c = brew(sugar=2)

Each call opens a fresh brew() box. Watch which values are filled in for you.

Practice default & keyword arguments

Exercise 1

Define power(base, exp=2) that returns base to the power exp.
Set result = power(exp=3, base=2) using keyword arguments (8).

Exercise 2

Define ticket(price, quantity=1, fee=0) returning price * quantity plus a single booking fee. Store booking by calling ticket with price 8, quantity 3, fee 2 using keyword arguments in any order.

Exercise 3

Define shipping(weight, rate=3, express=False). Base shipping is weight * rate; express adds a flat 5. Store quote for weight 2, rate 4 and express True using keywords. Zero weight still pays the express fee if requested.

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Practice

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Visualizer Watch your code run line by line

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Memory · names → values

Variables appear here as Python creates them.

Output & plots