791. Custom Sort String - LeetCode Solution

class Solution:
    def customSortString(self, S: str, T: str) -> str:
        
        a = ""
        l = list(T)
        
        for i in range(len(S)):
            for j in range(len(l)):
                if S[i] == l[j]:
                    a = a + T[j]
                    l[j] = ""
        
        
        l = "".join(l)
        return a+l