Python Basics · Functions · Lesson 12 of 36
Parameters and Default Values
Concept
Parameters and Default Values
Function parameters can have default values, which are used automatically when no argument is passed.
Parameters with defaults must come after parameters without defaults in the function signature, or Python raises a syntax error.
By the end of this lesson
- Explain the core idea behind Parameters and Default Values.
- Predict output before running a change.
- Test one realistic and one unusual input.
- Use the result to make the next decision.
How to study this page
- 1. Read one concept.
- 2. Change the example.
- 3. Run, compare, and explain.
- 4. Complete the challenge below.
Syntax
def function_name(param=default_value):
return valueExampleRunnable
def greet(name="friend"):
return f"Hi, {name}!"
print(greet())
print(greet("Alex"))Self-check before continuing
Without looking at the example, describe what changes when you modify one input in Parameters and Default Values. Then reopen the editor and prove your explanation with a small test.
You are ready to continue when you can predict, test, and explain the result.
Your turn
Write a function with a default parameter for a discount percentage.
Loading editor…
Console