Permutation of a string backtracking

def permute(s):
    s=list(s)
    n,ans=len(s),[]
    def dfs(i):
        if i==n-1:
            ans.append(''.join(s))
            return
        # we will swap indices from i+1 to n with i and do backtrack. This ensures generations of diff permutatations
        #In recursion level 1 we do swapping from 0th index to  (0+1,n) indices
        #in recursion level 2 we do swapping from 1st index to (1+1,n) indices
        #in recursion level ith we do swaping from ith index to (i+1,n) indices
        for j in range(i+1,n):
            s[i],s[j]=s[j],s[i]
            dfs(i+1)
            s[i],s[j]=s[j],s[i]
    dfs(0)
    return ans
permute("shpdwa")