Welcome! In today's lesson, we'll delve into a unique coding challenge that centers around traversing the digits of a number using a while loop under a specific condition. You'll have the opportunity to practice and enhance your skills in working with Python's loops and conditional statements - fundamental concepts in programming. Are you as excited as I am? Let's dive in!

Today, our objective is to create a function that operates on an integer input. The task might seem simple, but it requires some ingenuity. Here's the mission: given an integer, n, we need to calculate and return the sum of its even digits — and here's the clincher — without converting n into a string. For instance, if n equals 4625, the output should be 12 because the sum of the even digits 4, 6, and 2 equals 12.

Keep in mind that n will always be a positive integer between $1$ and $10^8$. Ready to give it a shot? Great! Let's get started!

To start, we need the basic structure of our function, where we begin by defining a variable digit_sum to keep track of the sum of even digits.

Below is the initial platform for our function:

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1def solution(n):
2    digit_sum = 0
3    # Our code will evolve from here

The tool we've chosen to traverse through the digits of the input integer n is the while loop, which is set to run as long as n is greater than zero. Let's incorporate this into our function:

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1def solution(n):
2    digit_sum = 0
3    while n > 0:
4        # We'll develop our function from here

Inside our loop, we'll first extract the last digit of n using the modulo operation (n % 10). If the digit is even, we'll increase our digit_sum by this digit.

After processing a digit, we'll then chop off the last digit of n using integer division (n // 10), which allows the while loop to proceed to the next digit. Here's how this appears in the code:

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1def solution(n):
2    digit_sum = 0
3    while n > 0:
4        digit = n % 10
5        if digit % 2 == 0:  # Check if the digit is even
6            digit_sum += digit
7        n = n // 10  # Remove the last digit

After summing up all the even digits, the final step is to return our digit_sum.

Our complete function now looks like this:

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1def solution(n):
2    digit_sum = 0
3    while n > 0:
4        digit = n % 10
5        if digit % 2 == 0:  # Check if the digit is even
6            digit_sum += digit
7        n = n // 10  # Remove the last digit
8    return digit_sum

Well done on completing this lesson! You've successfully navigated the foundational concepts of using a while loop to traverse the digits of a number and have gained an understanding of how to apply conditions within it. Now, it's your turn to apply what you've learned. I invite you to explore additional challenges to solidify and build upon your new skill set. Remember, the only limit to your growth is the boundary of your dedication. Keep practicing; your Python prowess is growing with each challenge you conquer!