Tự nhiên

 Permutation function 

1. def permute(s):
2.     n = len(s) 
3.     if n <= 1: 
4.         return s
5.     elif n == 2:
6.         return [''.join([s[0],s[1]]),''.join([s[1],s[0]])]
7.     else:# n > 2
8.         snew = []
9.         for i in range(n):
10.             a = [k for k in s]#copy s to a
11.             #print(s)
12.             ele = a.pop(i)
13.             for p in permute(a):
14.                 q = ele + p
15.                 if not(q in snew):
16.                     snew.append(q) 
17.         return snew
18. 
    
19. def permutations(string):
20.     s = [ele for ele in string]
21.     return permute(s)

This code is not efficientcy

Using set() in python rather list()

def permutations(string):
  if len(string) == 1: return set(string)
  first = string[0]
  rest = permutations(string[1:])
  result = set()
  for i in range(0, len(string)):
    for p in rest:
      result.add(p[0:i] + first + p[i:])
  return result

Or intertool library:

import itertools

def permutations(string):
    return list("".join(p) for p in set(itertools.permutations(string)))