Python – Extract indices of Present, Non Index matching Strings

Given two strings, extract indices of all characters  from string 1 which are present in other string, but not in same index.

Input : test_str1 = ‘pplg’, test_str2 = ‘pineapple’
Output : [0, 1, 2]
Explanation : ppl is found in 2nd string, also not on same index as 1st.

Input : test_str1 = ‘pine’, test_str2 = ‘pineapple’
Output : []
Explanation : Found in other string on same index.

Method #1 : Using enumerate() + loop

In this, we employ nested loop to check for each character its occurrence in 2nd string, and then if it’s in other position, if found the index is appended.

Python3

# Python3 code to demonstrate working of
# Extract indices of Present, Non Index matching Strings
# using loop + enumerate()

# initializing strings
test_str1 = 'apple'
test_str2 = 'pineapple'

# printing original Strings
print("The original string 1 is : " + str(test_str1))
print("The original string 2 is : " + str(test_str2))

# the replaced result
res = []
for idx, val in enumerate(test_str1):

    # if present in string 2
    if val in test_str2:

        # if not present at same index
        if test_str2[idx] != val:
            res.append(idx)

# printing result
print("The extracted indices : " + str(res))

Output

The original string 1 is : apple
The original string 2 is : pineapple
The extracted indices : [0, 1, 2, 3, 4]

Method #2 : Using enumerate() + zip() + list comprehension

In this, we perform the task of getting indices using enumerate() and pairing of both strings is done using zip(), the conditional checks occur using list comprehension.

Python3

# Python3 code to demonstrate working of
# Extract indices of Present, Non Index matching Strings
# using enumerate() + zip() + list comprehension

# initializing strings
test_str1 = 'apple'
test_str2 = 'pineapple'

# printing original Strings
print("The original string 1 is : " + str(test_str1))
print("The original string 2 is : " + str(test_str2))

# one-liner to solve this problem.
res = [idx for idx, (x, y) in enumerate(zip(test_str1, test_str2)) if x != y and x in test_str2]

# printing result
print("The extracted indices : " + str(res))

Output

The original string 1 is : apple
The original string 2 is : pineapple
The extracted indices : [0, 1, 2, 3, 4]