Easy Roman Numeral Conversion | Python Project

Table of Contents

1. Introduction
2. Understanding Roman Numerals
3. The Conversion Process
4. Implementing the Conversion Function
5. Testing the Function
6. Conclusion

Article

Introduction

Welcome to Project Python! In this series, I, a coding enthusiast, take on various coding challenges to challenge my coding skills and share my learnings along the way. Each episode focuses on a different problem, and in this episode, we will tackle the task of creating a function that can convert any number into its equivalent Roman numeral.

Understanding Roman Numerals

Roman numerals are a number system that originated in ancient Rome. They use letters to represent numbers, and each letter has a specific value. Here is a list of Roman numerals and their corresponding values:

• M represents 1000
• D represents 500
• C represents 100
• L represents 50
• X represents 10
• V represents 5
• I represents 1

However, Roman numerals also follow an additional rule where one letter can only appear three times in a row. This means that certain numbers, like 4, 9, 40, 90, 400, and 900, have a different representation.

The Conversion Process

To convert a number to its equivalent Roman numeral, we follow a simple process. Let's use the number 1249 as an example.

1. Find the largest number from the list of Roman numerals that is less than or equal to the given number. For 1249, the largest number is 1000, represented by the letter M.
2. Write down the corresponding Roman numeral (M) and subtract the value (1000) from the given number (1249). This leaves us with 249.
3. Repeat steps 1 and 2 with the remaining number. The largest number less than or equal to 249 is 100, represented by the letter C. Write down the Roman numeral (C) and subtract the value (100) from 249, resulting in 149.
4. Repeat steps 1 and 2 once again. The largest number less than or equal to 149 is 100 (C) again. Write down another C and subtract 100 from 149, leaving us with 49.
5. The largest number less than or equal to 49 is 40, represented by the letters XL. Write down XL and subtract 40 from 49, resulting in 9.
6. Finally, the largest number less than or equal to 9 is 9 itself, represented by the letters IX. Write down IX and subtract 9 from 9, leaving us with 0.
7. At this point, the conversion is complete, and the letters we wrote down in the process form our Roman numeral. In this case, the Roman numeral for 1249 is MCCXLIX.

We can generalize this process as follows:

1. Find the largest number from the list of Roman numerals that is less than or equal to the given number.
2. Write down the Roman numeral representation and subtract its value from the given number.
3. Repeat steps 1 and 2 until the given number is equal to 0.

Implementing the Conversion Function

Now that we understand Roman numerals and the conversion process, let's start coding the function. We will define a function called to_roman() that takes a single integer as input and returns a string containing the Roman numeral representation.

To implement the function, we will follow these steps:

1. Define the function using the def keyword and the name to_roman().
2. Create two lists: one containing the Roman numerals (in the same order as discussed earlier) and another containing their corresponding values.
3. Initialize a variable i to a value of 12. This will help us iterate through the lists in reverse order.
4. Create a variable roman_numeral and set it as an empty string. This will hold our answer.
5. Create a while loop that runs as long as the given number is not equal to 0.
   • Inside the loop, check if the value at index i in the list of numbers is less than or equal to the given number. If true, add the corresponding Roman numeral to roman_numeral and subtract the value from the given number.
   • If the condition is not true, decrease the value of i by 1.
6. Once the loop terminates (i.e., the given number is equal to 0), the conversion is complete. Return the roman_numeral.

Testing the Function

To ensure that our function works correctly, let's test it with various values. For example, let's call our to_roman() function with the value of 49. The expected output is "XLIX," which is the Roman numeral representation of 49.

Conclusion

In this episode of Project Python, we tackled the challenge of creating a function to convert numbers into their equivalent Roman numerals. We learned about the history and rules of Roman numerals, as well as the step-by-step conversion process. By implementing the to_roman() function, we can now easily convert any number into its Roman numeral representation.