On Monday, April 1, 2013 8:00:30 PM UTC-4, Steven D'Aprano wrote:
> On Mon, 01 Apr 2013 14:44:45 -0700, khaosyt wrote:
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> > If I wanted to get the sum of some numbers (for example: 1 + 2 + 3 + 4 +
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> > 5 = 15) from the attached program what do I do? Keep in mind that the
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> > print statement prints the integers individually.
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> Yes, we know what the print statement does. Some of us have been using
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> Python for weeks now.
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> Some comments interspersed within your code below:
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> > integer = 0
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> > denom = 10
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> > again = "y" #sentinel:
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> Technically, that's not a sentinel.
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> > while again == "y" or again == "Y":
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> > integer = input("Enter a positive integer: ")
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> I believe that the last time you asked this question, you were told not
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> to use the "input" function as it was dangerous or can lead to hard-to-
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> understand bugs. Change the above line to:
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> integer = raw_input("Enter a positive integer: ")
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> Notice that if you do this, the so-called "integer" is actually a string.
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> This is a good thing! You want it as a string, since that makes it easy
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> to extract individual digits.
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> > while denom <= integer:
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> > denom = denom*10
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> > while denom > 1:
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> > denom = denom/10
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> > number = integer/denom
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> > integer = integer%denom
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> > print str(number)
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> All this stuff with denom seems to be aimed at extracting the digits from
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> a number. There's an easier way: just work with the string.
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> After the line I suggested above
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> integer = raw_input("Enter a positive integer: ")
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> "integer" is a string of digits. So you can iterate over the digits using
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> a for-loop:
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> # this is not what you want!
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> for digit in integer:
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> print digit
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> Instead of printing the digits, you want to add them up. So start by
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> initialising a total, then add them:
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> total = 0
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> for digit in integer:
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> total = total + digit
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> Warning! The above three lines contains a bug. If you make the changes I
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> suggest, and try it, you will get an error. That's okay. Read the error.
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> Try to understand what it is telling you. Hint: remember that total is an
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> actual int, a number, while each digit is a single character, a string.
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> You need to convert each digit into a number before adding it. Hint: the
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> int function takes a string, and converts it to a number.
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> py> 42 + "23"
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> Traceback (most recent call last):
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> File "<stdin>", line 1, in <module>
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> TypeError: unsupported operand type(s) for +: 'int' and 'str'
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> py> 42 + int("23")
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> 65
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> This should hopefully give you enough information to get some working
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> code. Try to write as much of the code as you can, and come back with any
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> further questions *after* making a good effort.
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> Another hint: try experimenting at the interactive interpreter, or IDLE.
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> If you're unsure about something, try it and see what happens *before*
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> asking.
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> Good luck.
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> --
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> Steven
Thanks. I'll try it out.
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