Python program to find the character position of Kth word from a list of strings

When it is required to find the character position of Kth word from a list of strings, a list comprehension along with enumerate() is used to get the position of each character when all strings are concatenated.

Example

Below is a demonstration of the same ?

my_list = ["python", "is", "fun", "to", "learn"]

print("The list is :")
print(my_list)

K = 15
print("The value of K is :")
print(K)

my_result = [element[0] for sub in enumerate(my_list) for element in enumerate(sub[1])]

my_result = my_result[K]

print("The result is :")
print(my_result)

Output

The list is :
['python', 'is', 'fun', 'to', 'learn']
The value of K is :
15
The result is :
2

How It Works

Let's break down the list comprehension step by step to understand how it finds character positions:

my_list = ["python", "is", "fun", "to", "learn"]

# Step 1: enumerate(my_list) gives word positions and words
print("Words with their positions:")
for word_pos, word in enumerate(my_list):
    print(f"Position {word_pos}: '{word}'")

print("\nCharacter positions when all strings are concatenated:")
# Step 2: For each word, enumerate characters to get their positions
char_positions = []
for word_pos, word in enumerate(my_list):
    for char_pos, char in enumerate(word):
        char_positions.append((word_pos, char_pos, char))
        print(f"Word {word_pos}, Char {char_pos}: '{char}'")

# The list comprehension extracts word positions for each character
result_positions = [word_pos for word_pos, word in enumerate(my_list) for char_pos, char in enumerate(word)]
print(f"\nWord positions for each character: {result_positions}")
print(f"15th character belongs to word at position: {result_positions[15]}")

Words with their positions:
Position 0: 'python'
Position 1: 'is'
Position 2: 'fun'
Position 3: 'to'
Position 4: 'learn'

Character positions when all strings are concatenated:
Word 0, Char 0: 'p'
Word 0, Char 1: 'y'
Word 0, Char 2: 't'
Word 0, Char 3: 'h'
Word 0, Char 4: 'o'
Word 0, Char 5: 'n'
Word 1, Char 0: 'i'
Word 1, Char 1: 's'
Word 2, Char 0: 'f'
Word 2, Char 1: 'u'
Word 2, Char 2: 'n'
Word 3, Char 0: 't'
Word 3, Char 1: 'o'
Word 4, Char 0: 'l'
Word 4, Char 1: 'e'
Word 4, Char 2: 'a'
Word 4, Char 3: 'r'
Word 4, Char 4: 'n'

Word positions for each character: [0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 2, 3, 3, 4, 4, 4, 4, 4]
15th character belongs to word at position: 4

Alternative Approach

Here's a more readable way to achieve the same result:

def find_word_position(string_list, k):
    """Find which word the Kth character belongs to when strings are concatenated."""
    char_count = 0
    
    for word_index, word in enumerate(string_list):
        char_count += len(word)
        if k < char_count:
            return word_index
    
    return -1  # K is beyond the total length

my_list = ["python", "is", "fun", "to", "learn"]
K = 15

result = find_word_position(my_list, K)
print(f"The {K}th character belongs to word at position: {result}")
print(f"The word is: '{my_list[result]}'")

The 15th character belongs to word at position: 4
The word is: 'learn'

Conclusion

The list comprehension approach uses nested enumerate() to map each character position to its corresponding word index. This technique is useful when you need to find which word a specific character belongs to in a concatenated string sequence.