Re: Flubbed it in the second interation through the string: range error... HOW?

On 5/29/2024 10:59 AM, MRAB via Python-list wrote:

On 2024-05-29 15:32, Thomas Passin via Python-list wrote:

On 5/29/2024 8:55 AM, Kevin M. Wilson wrote:

Please recall, I said the format for the email failed to retain the proper indents.
I'll attach a picture of the code!
Purpose; to uppercase every other letter in a string.
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Thanks all, KMW

>
Simpler is good, and readability is good.  For a simple conversion that
has a little touch of generality:
>
s1 = 'this is a test'
def convert(i, ch):
      return ch.upper() if i % 2 else ch
>
result = ''.join([convert(i, ch) for i, ch in enumerate(s1)])
print(result)  # tHiS Is a tEsT
>

[snip]
Small mistake there. The original code converted to uppercase on even indexes, whereas your code does it on odd ones.

I wondered if anyone would catch that :)  Anyway, I don't think the original question was whether to start with even or odd but ways to iterate character by character and do something, right?

However, this has a weakness: what to do about spaces.  Should they be
counted among the characters to be uppercased? or should they not be
included in the count of the alternation?  If you want to uppercase
every other letter that is not a space, things become a little more
complicated.  And then do you want this to apply to all whitespace or
only spaces?
>
If you want to skip changing spaces, then you need to track the state of
converted characters in some way.  It would probably be easier (and more
readable) to use a "for x in t:" construction:

Actually, I did mess up the action for a space.  It should be:
def convert(convert_this, ch):
     """Convert character ch if convert_this is True.
     Don't convert spaces.
     """
     if ch == ' ':
        return (convert_this, ch)
     if convert_this:
        return (False, ch.upper())
     return (True, ch)
We should never get two printable uppercased characters in a row, even if there is a space between them, but my original convert(convert_this, ch) did.

def convert(convert_this, ch):
      """Convert character ch if convert_this is True.
      Don't convert spaces.
      """
      if convert_this:
          if ch == ' ':
              return (convert_this, ch)
          elif convert_this:
              return (False, ch.upper())
      return (True, ch)
>
convert_next = False
result = ''
for ch in s1:
      convert_next, ch = convert(convert_next, ch)
      result += ch
print(result)  # tHiS Is A TeSt
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There could be even more complications if you allow non-ascii characters
but you were asking about processing character by character so I won't
get into that.
>
(You haven't specified the problem in enough detail to answer questions
like those).
>

[snip]