#7 Learning Python Functions

Today, I reviewed the basics of functions in Python.
Function is simply “a named block of code that performs a specific task.”
Once defined, a function can be reused as many times as you want—this makes your code cleaner and more efficient.
In Python, you define a function using the keyword def.
Here are some examples I practiced today.

1. Function to Return the Average of Two Numbers

def average(a, b):
    result = (a + b) / 2
    return result

ave = average(3, 8)
print(f"The average is {ave}.\n")

2. Function to Determine Whether a Number Is Even or Odd

def check_even(num):
    if num % 2 == 0:
        return "偶数です"
    else:
        return "奇数です"

che = check_even(9)
print(f"The result is {che}.\n")

3. Function to Return the Sum of a List

def sum_list(nums):
    result = 0
    for n in nums:
        result += n
    return result

result = sum_list([3, 5, 8, 2])
print(f"The total is {result}.\n")

In the final problem, I combined function definitions with for loops and list operations.
This allowed me to perform data filtering—selecting only the necessary data from a larger set. This concept is deeply connected to real-world web applications: for example, displaying only unread emails in a mail app or showing only in-stock items on an e-commerce site.

When I can relate what I learn in Python to everyday tools and services, my understanding deepens and my motivation grows.