背景：学习《Python基础教程第2版》，第10.3章 标准库：一些最爱 时，

运行如下例子：

用户选择投掷的骰子数以及每个骰子具有的面数，随机返回骰子的点数，代码如下：

from random import randrange

num = input('How many dice? ')

sides = input('How many sides per die? ')

sum = 0

for i in range(num):sum += randrange(sides) + 1

print( 'The result is ',sum)

运行之后报如下错误：

=================== RESTART: D:/Python/my_program/dice.py ===================

How many dice? 3

How many sides per die? 6

Traceback (most recent call last):

File "D:/Python/my_program/dice.py", line 21, in for i in range(num):sum += randrange(sides) + 1

TypeError: 'str' object cannot be interpreted as an integer

分析错误提示是说不能把str类型的对象当成int类型用

for语句中用到了num,sum,sides三个变量，分析发现sum肯定是int型，而num和sides都是input传入的，那问题肯定出在input函数上，于是通过编码验证：

>>> a = input ('How many dice?')

How many dice?3

>>> a

'3'     ------ 由此可见，input输入的是字符串类型的值

查找资料发现：

python3.x版本中，舍弃了raw_input函数，只保留了input( )函数，其接收任意输入，将所有输入默认为字符串处理，并返回字符串类型

因此，上述代码要运行成功，需修改如下：

from random import randrange

num = int(input('How many dice? '))   ---- 强制转换成想要的类型

sides = int(input('How many sides per die? '))

sum = 0

for i in range(num):sum += randrange(sides) + 1

print( 'The result is ',sum)

再次运行通过：

=================== RESTART: D:/Python/my_program/dice.py ===================

How many dice? 5

How many sides per die? 6

The result is  15