python non recursive full permutation implementation

I'm just getting started with python, and I'm currently looking at the functions section 1. Combined with the array operation, write a non - recursive full array generation. The principle is the insertion method, that is, in an existing arrangement with n elements, the elements added after are inserted in each position of the first, middle and last in order to generate n+1 new full arrangement. Because Python is easy to cut arrays or strings and merge, the program saves a lot of code.

def getArrayInsertCharToStr(STR,CHAR):
  arr =[]
  s_len = len(STR)
  index =0
  while index <= s_len:
    # Split string 
    arr.append(STR[:index]+CHAR+STR[index:s_len])
    index = index + 1
  return arr  

def getArrayInsertCharToArray(array,CHAR):
  index = 0
  re_array = []
  while index < len(array):
    re_array = re_array + getArrayInsertCharToStr(array[index],CHAR)
    index = index + 1
  return re_array       

def getPermutation(STR):
    resultArr = [STR[0]]
    for item in STR[1:]:
      resultArr = getArrayInsertCharToArray(resultArr,item)
    return   resultArr


print(getPermutation('abc'))