Python Function Parameters & Arguments
Parameters are like input slots in a toaster: you put in sourdough bread, you get toasted sourdough. You put in a bagel, you get a toasted bagel. Default values let you specify fallbacks when no input is provided.
"Imagine a calculator function add(a, b). Instead of only adding 2 + 2 forever, parameters a and b let you pass any two numbers in the universe and get the right answer."
Deep Dive: How It Works
Parameters vs Arguments: Parameters are the variable names in the function definition (def greet(name):). Arguments are the actual concrete values passed during the call (greet("Alex")).
Multiple Parameters: Separate parameters with commas: def calculate_total(price, tax_rate, discount):.
Default Parameter Values: You can assign default values: def connect(host="localhost", port=8080):. If the caller does not pass those arguments, Python uses the defaults.
Positional vs Keyword Arguments: You can pass arguments positionally (in order), or by explicit name: connect(port=9000, host="127.0.0.1").
Syntax Blueprint
def greet(name, title="Developer"):
print(f"Hello {title} {name}!")
greet("Ada") # Uses default title
greet("Alan", title="Dr.") # Overrides titleDefault parameters must always be placed AFTER parameters without defaults.
Core Rules to Remember
Common Beginner Traps & How to Fix Them
Placing default parameters before non-default parametersWhy it happens: Writing def test(a=1, b): causes a SyntaxError because Python cannot tell which argument was passed.
How to fix: Always put parameters with defaults at the end of the parameter list.
Live Interactive Example
Hit Run Code to see it liveYour Turn: Micro Challenge
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Create a function with parameters
- Define a function multiply(a, b) that prints the product of a * b.
- Call multiply(6, 7).
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