Question 392 Is Subsequence

The code is in the following link:

https://leetcode.com/problems/is-subsequence/

My code:

class Solution:
    def isSubsequence(self, s: str, t: str) -> bool:
        if len(s) == 0:
            return True
        elif len(t) == 1:
            if s[0] == t[0]:
                return True
            else:
                return False
        else:
            i = 0
            CheckNum = 0
            while i< len(t):
                if s[CheckNum] == t[i]:
                    CheckNum +=1
                if CheckNum == len(s):
                    return True
                i+=1
            return False

Explanation:

Check one by one, if one element is confirmed, then we check next element in the string s. If the total all the element in the string s occur in string t, then we return true, otherwise we return false.