Parameters

Right now, the greet function always prints the same message. What if you want it to greet different people? That’s what parameters are for — they let you pass data into a function so it can work with different values each time.

Adding a parameter

You add a parameter by putting a name inside the parentheses when you define the function:

def greet_user(name):
    print(f"Hello, {name}! Welcome to Python!")

name is a parameter — a placeholder for the value you’ll pass in when you call the function.

Passing an argument

When you call the function, the value you pass in is called an argument:

greet_user("Alice")  # Output: Hello, Alice! Welcome to Python!
greet_user("Bob")    # Output: Hello, Bob! Welcome to Python!

Each time you call greet_user, you pass in a different argument, and the function uses it for name. Same function, different results.

Multiple parameters

A function can have more than one parameter — just separate them with commas:

def describe_pet(name, animal):
    print(f"{name} is a {animal}.")
 
describe_pet("Rex", "dog")   # Output: Rex is a dog.
describe_pet("Nemo", "fish") # Output: Nemo is a fish.

Arguments are matched to parameters in order — the first argument goes to the first parameter, the second to the second, and so on.

Default values

You can give a parameter a default value. If the caller doesn’t pass that argument, Python uses the default:

def greet_user(name, greeting="Hello"):
    print(f"{greeting}, {name}!")
 
greet_user("Alice")        # Output: Hello, Alice!
greet_user("Alice", "Hi")  # Output: Hi, Alice!

Parameters with defaults must come after parameters without defaults.

Try it out