Strange behaviour with a for loop.

[Sean Murphy]

Chris,

Thanks for the tip on the function. I was not aware of that function, Grin. Creating the function as you mention makes a lot of sense.

I am doing a lot of little bits and pieces focusing on things I need to eventually build a script that is going to compile data from a router and config it. 

I have hundreds of other questions, if I don't find answers on the net before hand.

Sean 
On 04/01/2014, at 6:52 PM, Cameron Simpson <cs at zip.com.au> wrote:

> On 04Jan2014 16:54, Sean Murphy <mhysnm1964 at gmail.com> wrote:
>> Thanks everyone.
>> 
>> Mark thanks for the correction on the ':'. Since I didn't cut and copy, rather typed it out. Errors crept in. :-)
>> 
>> another question in relation to slicing strings. If you want to get a single character, just using the index position will get it. If I use the following, shouldn't it also work? when I use Python 3.3, it didn't provide anything.
>> 
>> a = "test.txt"
>> print a[3]
>> result is:
>> 
>> 't
> 
> As expected, yes?
> 
>> print a[3:1]
>> Nothing is printed. 
>> 
>> print a[3:2]
>> Nothing is printed.
> 
> These are not requests for 1 and 2 character strings. They are
> requests for the character in the span from, respectively, 3 to 1
> and from 3 to 2. Important: counting FORWARDS. So: zero length
> strings.
> 
>> print a[3:-1]
>> t.tx is printed.
>> 
>> Why doesn't the positive number of characters to be splice return anything while the negative value does?
> 
> -1 is shorthand for len(a)-1
> It is often convenient to refer to a position from the end of the
> array instead of the start.
> 
> So this means: [3:7], so positions 3,4,5,6.
> 
>> sorry about these basic questions. I do like the splice feature within Python. Also what is the best method of testing for a blank string?
> 
> Well, and empty string: a == '' or len(a) == 0.
> And, because an "if" tests the nonzeroness of a single argument and
> an empty string has length zero, you can also go:
> 
>  if a:
>    print "long string", a
>  else:
>    print "empty string"
> 
> OTOH, if you mean a "blank string" to mean "containing only
> whitespace", you can use the string method "isspace", which tests
> that all characters are whitespace and that the string is not empty.
> The doco for isspace() actually says:
> 
>  Return true if there are only whitespace characters in the string
>  and there is at least one character, false otherwise.
> 
> So you might write:
> 
>  if not a or a.isspace():
>    print "blank string:", repr(a)
> 
> Really you'd want to put that it a (trivial) function:
> 
>  def isblank(s):
>    ''' Test that the string `s` is entirely blank.
>    '''
>    return not s or s.isspace()
> 
> That way you can write isblank() all through your program and control the
> precise meaning by modifying the function.
> 
> Cheers,
> -- 
> 
> The perl5 internals are a complete mess. It's like Jenga - to get the perl5
> tower taller and do something new you select a block somewhere in the middle,
> with trepidation pull it out slowly, and then carefully balance it somewhere
> new, hoping the whole edifice won't collapse as a result.
> - Nicholas Clark, restating an insight of Simon Cozens