Python实现把数字转换成中文

周末在家，写了个小程序，用于将阿拉伯数字转换化大写中文。程序没经过任何优化，出没经过详细的测试，挂到网上，方便将来有需要的时候直接拿来用。

#!/usr/bin/python
#-*- encoding: utf-8 -*-

import types

class NotIntegerError(Exception):
  pass

class OutOfRangeError(Exception):
  pass

_MAPPING = (u'零', u'一', u'二', u'三', u'四', u'五', u'六', u'七', u'八', u'九', )
_P0 = (u'', u'十', u'百', u'千', )
_S4, _S8, _S16 = 10 ** 4 , 10 ** 8, 10 ** 16
_MIN, _MAX = 0, 9999999999999999

def _to_chinese4(num):
  '''转换[0, 10000)之间的阿拉伯数字
  '''
  assert(0 <= num and num < _S4)
  if num < 10:
    return _MAPPING[num]
  else:
    lst = [ ]
    while num >= 10:
      lst.append(num % 10)
      num = num / 10
    lst.append(num)
    c = len(lst)  # 位数
    result = u''

    for idx, val in enumerate(lst):
      if val != 0:
        result += _P0[idx] + _MAPPING[val]
        if idx < c - 1 and lst[idx + 1] == 0:
          result += u'零'

    return result[::-1].replace(u'一十', u'十')

def _to_chinese8(num):
  assert(num < _S8)
  to4 = _to_chinese4
  if num < _S4:
    return to4(num)
  else:
    mod = _S4
    high, low = num / mod, num % mod
    if low == 0:
      return to4(high) + u'万'
    else:
      if low < _S4 / 10:
        return to4(high) + u'万零' + to4(low)
      else:
        return to4(high) + u'万' + to4(low)

def _to_chinese16(num):
  assert(num < _S16)
  to8 = _to_chinese8
  mod = _S8
  high, low = num / mod, num % mod
  if low == 0:
    return to8(high) + u'亿'
  else:
    if low < _S8 / 10:
      return to8(high) + u'亿零' + to8(low)
    else:
      return to8(high) + u'亿' + to8(low)

def to_chinese(num):
  if type(num) != types.IntType and type(num) != types.LongType:
    raise NotIntegerError(u'%s is not a integer.' % num)
  if num < _MIN or num > _MAX:
    raise OutOfRangeError(u'%d out of range[%d, %d)' % (num, _MIN, _MAX))

  if num < _S4:
    return _to_chinese4(num)
  elif num < _S8:
    return _to_chinese8(num)
  else:
    return _to_chinese16(num)

if __name__ == '__main__':
  print to_chinese(9000)