[Tutor] Checksum program

[taserian]

On Wed, Mar 23, 2011 at 9:09 AM, Lezlie Kline <lezlie.kline at gmail.com>wrote:

> Hi,
>
> I'm trying to work out the bugs in a program for calculating the checksum
> (modulo 256) of an input string.  I'm testing it with my full name and I'm a
> beginner with Python.  Here's what I have so far.
>
> def main():
>     print"This program creates a checksum for a message."
>     name=raw_input("Please enter the message to encode: ")
>     message=name
>     output=name
>     for i in range(len(message)):
>         print"The value of message[i] is ", message[i]
>         output=output+name+ord(message[i])
>         print"The value of the message is ", output
>     checksum=(output)%256
>     print"The checksum is ", checksum
>
> main()
>
I'd like to give you some pointers so you can solve it yourself:

What's the checksum for a completely empty message (i.e., no characters at
all)?
Where are you storing the (ASCII) values of each letter? Has it been
initialized properly?


> I know I'm offbase somewhere, but I'm not understanding some parts of the
> accumulator part of the program.  I need it to work with the message[i]
> intact.  In other words, I need the pseudo code to go something like this:
>
> print message
> get input
> find length
> using length in range function accumulate ASCII numbers
> calculate checksum
> print checksum
>
> I'd appreciate any help offered as I'm "pulling out my hair."


message[i] will provide you the character at position i. What are you doing
with it?

Tony R.
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