Split an integer into digits to compute an ISBN checksum

Question

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.

Answer 1

Just create a string out of it.

myinteger = 212345 number_string = str(myinteger) 

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

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

Or you can slice it:

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

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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) 

For more information read a tutorial.