将整数拆分为数字以计算ISBN校验和 [英] Split an integer into digits to compute an ISBN checksum

问题描述

我正在编写一个计算ISBN号校验位的程序。我必须将用户的输入（ISBN的九位数）读入整数变量，然后将最后一位数乘以2，将倒数第二位乘以3，依此类推。如何将整数拆分为其组成数字来执行此操作？由于这是一个基本的家庭作业，我不应该使用列表。

I'm writing a program which calculates the check digit of an ISBN number. I have to read the user's input (nine digits of an ISBN) into an integer variable, and then multiply the last digit by 2, the second last digit by 3 and so on. How can I "split" the integer into its constituent digits to do this? As this is a basic homework exercise I am not supposed to use a list.

推荐答案

只需创建一个字符串。

myinteger = 212345
number_string = str(myinteger)

这就够了。现在你可以迭代它：

That's enough. Now you can iterate over it:

for ch in number_string:
    print ch # will print each digit in order

或者你可以分割它：

print number_string[:2] # first two digits
print number_string[-3:] # last three digits
print number_string[3] # forth digit

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或者更好的是，不要将用户的输入转换为整数（用户输入一个字符串）

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Or better, don't convert the user's input to an integer (the user types a string)

isbn = raw_input()
for pos, ch in enumerate(reversed(isbn)):
    print "%d * %d is %d" % pos + 2, int(ch), int(ch) * (pos + 2)

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