input: Write a python function to pad the given string on both sides with the given padding character until the required length is reached.
  assert pad_str('Python', '*', 10) == '**Python**'
  assert pad_str('Data', '-', 8) == '--Data--'
  assert pad_str('Hello', '#', 9) == '##Hello##'
output: def pad_str(s, pad_char, total_length):
      pad_total = total_length - len(s)
      pad_side = pad_total // 2
      return pad_char * pad_side + s + pad_char * (pad_total - pad_side)