python3实现短网址和数字相互转换的方法

import math
import decimal
def convert_to_code(num):
  """
  将数字转换为代码
  """
  def get_num(num, out=''):
    num = decimal.Decimal(num)
    codes = "abcdefghjkmnpqrstuvwxyz23456789ABCDEFGHJKMNPQRSTUVWXYZ"
    if num > 53:
      key = num % 54
      num = math.floor(num / 54) - 1
      return get_num(num, codes[int(key)] + out)
    else:
      return codes[int(num)] + out
  return get_num(num)
def convert_to_num(code):
  """
  将代码转为数字
  """
  import math
  codes = "abcdefghjkmnpqrstuvwxyz23456789ABCDEFGHJKMNPQRSTUVWXYZ"
  num = 0
  num = decimal.Decimal(num)
  i = len(code)
  for char in code:
    i -= 1
    pos = codes.find(char)
    num += (54 ** i) * (pos + 1)
  num -= 1
  # 任意数的 0 次方等于1，所以需要减去
  return int(num)