Default parameters

Learn parameters with default values.

Default parameters

A parameter can have a default value; if not passed at the call, the default is used:

def greet(name, greeting="Welcome"):
    print(greeting, name)

greet("Alex")            # Welcome Alex
greet("Alex", "Hello")    # Hello Alex

Default parameters must be on the right; otherwise a SyntaxError is raised. This makes the call flexible.

Multiple defaults

Multiple parameters can have defaults:

def create_user(name, role="user", active=True):
    return {"name": name, "role": role, "active": active}

All right-hand parameters can have defaults. At the call you can skip any of them; they get their default value.

This simplifies the call in functions with many options.

Exercise Write a function with a default parameter

Define a function called greet with name and greeting (default "Hello") parameters that does print(greeting, name). Call it with greet("Ayse").

Show example solution

def greet(name, greeting="Hello"):
    print(greeting, name)
greet("Ayse")

Test yourself

Match default parameter features

greeting="Welcome"

Default value
on the right

Position
greet("Alex")

Call with default
SyntaxError

Error if on left

Complete the default parameter

def greet(name, greeting=____):
    print(greeting, name)

Show answer

def greet(name, greeting="Welcome"):
    print(greeting, name)

Which statement is correct?
- Default parameters go on the left
- Default parameters are not allowed
- Default parameters slow the function
- Default parameters go on the right
Show answer

Default parameters go on the right — Default parameters must go on the right; otherwise SyntaxError.

Next lesson: *args and **kwargs

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