Parameters and arguments in Python

Introduction

Parameters and arguments let you send information into a function so it can work with different data each time.

When you want a function to add two numbers you give it the numbers as arguments.

When you want to greet different people with the same function, you pass their names as arguments.

When you need to calculate the area of different rectangles, you send the width and height as arguments.

When you want to reuse a function but with different inputs each time.

When you want to keep your code organized by separating tasks into functions that take inputs.

Syntax

Python

def function_name(parameter1, parameter2):
    # code using parameters
    pass

function_name(argument1, argument2)

Parameters are the names inside the function definition.

Arguments are the actual values you send when calling the function.

Examples

This function takes one parameter name and prints a greeting using the argument "Alice".

Python

def greet(name):
    print(f"Hello, {name}!")

greet("Alice")

The function add takes two parameters and returns their sum. We call it with arguments 3 and 5.

Python

def add(a, b):
    return a + b

result = add(3, 5)
print(result)

This function has a default parameter animal_type. If no argument is given, it uses 'dog'.

Python

def describe_pet(pet_name, animal_type='dog'):
    print(f"I have a {animal_type} named {pet_name}.")

describe_pet('Buddy')
describe_pet('Whiskers', 'cat')

Sample Program

This program defines a function multiply with two parameters. It is called twice with different arguments to multiply numbers.

Python

def multiply(x, y):
    return x * y

result1 = multiply(4, 5)
result2 = multiply(7, 3)
print(f"4 times 5 is {result1}")
print(f"7 times 3 is {result2}")

Important Notes

Parameters are like placeholders; arguments are the real values you give.

You can have default values for parameters to make arguments optional.

Order matters: arguments are matched to parameters by position unless you use named arguments.

Summary

Parameters are names in function definitions to receive values.

Arguments are the actual values passed to functions when called.

Using parameters and arguments makes functions flexible and reusable.