Reverse String

using iterative method (two pointers)
class Solution:
    def reverseString(self, s: List[str]) -> None:
        """
        Do not return anything, modify s in-place instead.
        """
        l,r=0,len(s)-1
        while l<r:
           s[l],s[r]=s[r],s[l]
           l,r=l+1,r-1

  or using stack 
class Solution:
    def reverseString(self, s: List[str]) -> None:
        """
        Do not return anything, modify s in-place instead.
        """
        stack = []
        for i in s:
            stack.append(i)
        i=0
        while stack:
              s[i]=stack.pop()
              i+=1
or using recusrion 
class Solution:
    def reverseString(self, s: List[str]) -> None:
        """
        Do not return anything, modify s in-place instead.
        """
        def reversing (l,r):
            if l<r:
                s[l],s[r]=s[r],s[l]
                reversing(l+1,r-1)
        reversing(0,len(s)-1)