How to make a function return a list of indices of the characters in the second string that appears in the first string?

Question

def get_indices_from_the_second_string(string1, string2):
    \'\'\'(str, str) -> list of int
    >>> get_indices_from_the_second_string(\'AGTACACGTTAC\', \'         


        

Answer 1

def get_indices_from_the_second_string(string1, string2):
    acc = []
    s2_counter = 0
    for i, letter in enumerate(string1):
        if letter == string2[s2_counter]:
            acc.append(i)
            s2_counter += 1
            if len(acc) == len(string2):
                break
    return acc

a = get_indices_from_the_second_string('GAATTCCGTTAC', 'GAATTC')

Answer 2

Use the built in function zip, along with another built in enumerate

acc = []
for i, (a, b) in enumerate(zip(string1, string2)):
    if a==b:
        acc.append(i)
return acc

Answer 3

Remove lines

            i += 1
            r += 1

as for loops increase i and r automatically.

And then modify your code:

lower = 0                             # from this index will be string1 searched

for i in range(0, len(string2)):
    for r in range(lower, len(string1)):
        if string1[r] == string2[i]:
            acc.append(r)
            lower = r + 1             # indexes from 0 to r are already used
            break
        elif r == len(string1) - 1:   # last index did not match
            return acc
return acc

Answer 4

Oh, I see what you're doing.

def get_indices_from_the_second_string(string1, string2):
    acc = []
    string1_index = 0
    for char in string2:
        while string1[string1_index] != char:
            string1_index += 1
            if string1_index >= len(string1):
                return acc
        acc.append(string1_index)
        string1_index += 1
        if string1_index >= len(string1):
            return acc
    return acc