Python Program that print elements common at specified index of list elements

When working with a list of strings, you might need to find characters that appear at the same position across all strings. This can be achieved using list comprehension, the min() function, and a Boolean flag to track common characters.

Example

Below is a demonstration of finding common characters at each index position ?

my_list = ["week", "seek", "beek", "reek", 'meek', 'peek']

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

min_length = min(len(element) for element in my_list)

my_result = []

for index in range(0, min_length):
   flag = True
   for element in my_list:
      if element[index] != my_list[0][index]:
         flag = False
         break

   if flag:
      my_result.append(my_list[0][index])

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

Output

The list is :
['week', 'seek', 'beek', 'reek', 'meek', 'peek']
The result is :
['e', 'e', 'k']

How It Works

The algorithm follows these steps ?

• Find the minimum length among all strings to avoid index errors

• Iterate through each character position (index) up to the minimum length

• For each position, compare the character in all strings with the character at the same position in the first string

• If all characters at that position match, add the character to the result list

• Use a Boolean flag to track whether all characters at the current position are identical

Alternative Approach Using all()

Here's a more concise version using the all() function ?

my_list = ["week", "seek", "beek", "reek", 'meek', 'peek']

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

min_length = min(len(element) for element in my_list)

my_result = []
for index in range(min_length):
    if all(element[index] == my_list[0][index] for element in my_list):
        my_result.append(my_list[0][index])

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

The list is :
['week', 'seek', 'beek', 'reek', 'meek', 'peek']
The result is :
['e', 'e', 'k']

Conclusion

This approach efficiently finds common characters at corresponding positions across multiple strings. The min() function ensures we don't exceed the shortest string's length, while the Boolean flag or all() function helps identify matching characters at each index.