On Mon, 2003-06-30 at 14:20, Danny Yoo wrote:
>  > Here's what I've got for the second scenario:
>  >
>  > s = raw_input('Enter a name: ')
>  > x = 0
>  > while x >= 0:
>  >     print s[x]
>  >     x += 1
>  >
>  > The error is expected because the counter goes on beyond the number of
>  > characters in the string and runs out of stuff to print.
>  
>  
>  Hi Matthew,
>  
>  
>  Ok, so that means that we want:
>  
>  
>  ###
>  while some_expression_that_is_false_when_x_is_too_large:
>      print s[x]
>      x += 1
>  ###
>  
>  
>  
>  The expression that we have, right now:
>  
>      x >= 0
>  
>  is true as long as x is either positive or zero.  ("nonnegative").  The
>  only problem is that this will always be true: nothing in the loop's body
>  ever causes x to become negative.  *grin*
>  
>  
>  'x' is always increasing, hence our program breaks when it tries to print
>  nonexistant characters.  So we need to choose a different condition,
>  something that is true only until the index reaches the end of the word.
>  
>  
>  That is, instead of
>  
>  
>          "Matthew Richardson"
>          (------------------------------------------>
>          0                                        infinity
>  
>  
>  We want to bound x's range to just:
>  
>  
>          "Matthew Richardson"
>          (------------------)----------------------->
>          0                                        infinity
>  
>  
>  
>  In mathematical terms, we'd say that we'd like a half-open range,
>  
>  
>           0  <=  x   < length of "Matthew Ricahrdson"
>  
>  
>  And we'll find that the equivalent expression in Python is very similar to
>  this.  *grin*
>  
>  
>  I hope this gives some hints on how to correct the while 'condition'
>  expression.  Good luck!

I knew I should have paid more attention in math...

Anyway, here is what I've got based on your excellent direction:

s = 'something'
x = 0
while x < len(s):
    print s[x]
    x += 1

Which works great.  I'm still stuck on how to do Zak's method of
manipulating the string, but starting to feel better about 'while' now.

Thanks,
Matt

-- 
Matt Richardson
Instructional Support Technician
Department of Art
CSU San Bernardino



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