1. Code

class Solution:
    def isSubsequence(self, s: str, t: str) -> bool:
        for e in s:
            if e in t:
                # index(e) indicates the first e in a list
                idx = t.index(e)
                # make t short
                t = t[idx+1:]
            else:
                return False
        return True

2. Result

        Runtime : 24 ms(95.08%), Memory usage : 14 MB(95.27%)
        (Runtime can be different by a system even if it is a same code.)

Check out the my GitHub repo for more info on the code. If you have questions, you can leave a reply on this post.