n this exercise, you are given a three word phrase and an integer referencing one of the three words

n this exercise, you are given a three word phrase and an integer referencing one of the three words. Return the phrase with the reference word doubled.

Example:
“double_word(“one two three”, 3) –> “one two three three”
double_word(“cat dog fish”, 2) –> “cat dog dog fish”

def double_word(phrase, ref):
pass

The Correct Answer and Explanation is:

Sure! Here’s the correct Python function to solve the problem, followed by a detailed explanation:

def double_word(phrase, ref):
    # Split the phrase into words
    words = phrase.split()
    
    # Adjust the reference index to zero-based index
    index = ref - 1
    
    # Insert the referenced word again right after its original position
    words.insert(index + 1, words[index])
    
    # Join the words back into a single string and return
    return " ".join(words)

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Explanation (300+ words):

This problem requires taking a phrase composed of exactly three words and doubling one of those words based on a given reference number (ref). The reference number indicates which word (1, 2, or 3) in the phrase should be duplicated.

Let’s break down the problem step-by-step:

1. Input and output:
   • Input: A string phrase containing exactly three words separated by spaces, and an integer ref which can be 1, 2, or 3.
   • Output: A string where the word at position ref is duplicated immediately after itself.
2. Splitting the phrase:
   To manipulate individual words, we need to split the phrase into a list of words. Using Python’s split() method on the string creates a list of words. For example, "one two three".split() returns ["one", "two", "three"].
3. Indexing adjustment:
   In the problem, the ref is 1-based indexing, meaning ref=1 corresponds to the first word, ref=2 the second, and so on. Python lists, however, use 0-based indexing, so we adjust by subtracting 1 to find the correct index in the list: index = ref - 1
4. Duplicating the word:
   We want to insert a duplicate of the word at position index immediately after it. Python lists provide the insert() method, which inserts an element at a specified position. We insert the word at index + 1, which is right after the original word. For example, if index=1 (second word), inserting at position 2 duplicates the second word right after itself. words.insert(index + 1, words[index])
5. Rebuilding the phrase:
   After modifying the list, we convert it back into a string using " ".join(words). This joins all words with spaces in between.
6. Returning the result:
   The final string is returned from the function.

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Example walkthrough:

• Input: "cat dog fish", ref=2
• Split: ["cat", "dog", "fish"]
• Index: 2 - 1 = 1
• Insert "dog" at position 2: list becomes ["cat", "dog", "dog", "fish"]
• Join: "cat dog dog fish"
• Output: "cat dog dog fish"

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This solution works efficiently, is clear, and directly follows from the problem requirements. It can be easily extended for phrases longer than three words by removing the assumption on length. The key learning is handling 1-based versus 0-based indexing and using list insertions in Python.