Re: Two python issues

On 05/11/2024 15.48, Raymond Boute wrote:

L.S.,
 Python seem to suffer from a few poor design decisions regarding strings and lists that affect the elegance of the language.
 (a) An error-prone "feature" is returning -1 if a substring is not found by "find", since -1 currently refers to the last item. An example:
  >>> s = 'qwertyuiop'
 >>> s[s.find('r')]
'r'
 >>> s[s.find('p')]
'p'
 >>> s[s.find('a')]
'p'
 >>>
 If "find" is unsuccessful, an error message is the only clean option.
Moreover, using index -1 for the last item is a bad choice: it should be len(s) - 1 (no laziness!).
Negative indices should be reserved for elements preceding the element with index 0 (currently not implemented, but a must for orthogonal design supporting general sequences).
 (b) When using assignment for slices, only lists with the same length as the slice should be acceptable, otherwise an error should be given. Anything that re-indexes items not covered by the slice is against the essential idea of assignment. For changes that imply re-indexing (e.g., inserting a list longer than the slice), Python offers cleaner solutions.
 Comments are welcome.

To write the nested expression, s[s.find(...)] it
means you're 200% sure of what happens in case of
not found.
It could be -1 or None or [] or anything.
So, the really correct thing to do, since you know
what will happen in case of not found, is *not* to
write the nested form, but explicitly state what it
will happen.
r = s.find(...)
if r is good:
     s[r]
else:
     print('not found')
Which is much easier to read, to debug, etc.
To paraphrase someone: "If the length of a
program would be measured by the time needed
to understand it, some programs are too short
to be short."
bye,
--
piergiorgio