speech module

Stephen's speech module is broken. This module is responsible for his number pronunciation. He has to click to input all of the numerical digits in a figure, so when there are big numbers it can take him a long time. Help the robot to speak easier and quicker to his friends by writing his speech module. All the words in the string must be separated by exactly one space character.

Input: Integer number from 0 to 999.

Output: A string representation of this number.

简单来说，就是把输入的数字转换为文字。

需要注意的问题主要是：

1.零的处理，在末尾的时候，0不需要念出来。这个问题用判断是否整除来解决比较好，设置全局变量判断是否进入递归是吃力不讨好。

2.格式。每一个数字之间需要用空格隔开。

FIRST_TEN = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"] 
SECOND_TEN = ["ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"]
OTHER_TENS = ["twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"]
HUNDRED = "hundred"

def checkio(number):
    if number < 10:
        return FIRST_TEN[number]
    elif number >= 10 and number < 20:
        return SECOND_TEN[number - 10]
    elif number >= 20 and number < 100:
        if number % 10 != 0:
            return OTHER_TENS[number / 10 - 2] + " " + checkio(number % 10)
        else:
            return OTHER_TENS[number / 10 - 2]
    else:
        if number % 100 == 0:
            return FIRST_TEN[number / 100] + " " + HUNDRED
        else:
            return FIRST_TEN[number / 100] + " " + HUNDRED + " " + checkio(number % 100)