Re: Two python issues

Op 5/11/2024 om 15:48 schreef Raymond Boute via Python-list:

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:

This is IMO indeed not the best design decision. Fortunately there's an alternative: the "index" method on strings, which raises exception ValueError when the substring is not found, instead of returning -1. An example:
 >>> s = 'qwertyuiop'
 >>> s[s.index('p')]
'p'
 >>> s[s.index('a')]
Traceback (most recent call last):
   File "<pyshell#3>", line 1, in <module>
     s[s.index('a')]
ValueError: substring not found

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).

I don't agree, I think this is a case of "practicality beats purity". Being able to use negative indices to index from the end is often very useful in my experience, and leads to code that is much easier to grok. General sequences on the other hand is a concept that I don't see ever implemented in Python (or most other programming languages AFAIK). I think it would be wrong to avoid implementing a feature that's very useful in practice in order to keep the door open for a theoretical feature that's probably not even wanted in the language.

(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.

Again I don't agree. I don't see anything wrong with replacing a part of a list with something that's longer, or shorter, or even empty. It's very practical, and I don't see how it's against the essential idea of assignment (or actually I'm not even sure what you mean by that).
Two closing remarks:
(1) I think that Python indeed has some warts, inconsistencies, gotchas. I think this is unavoidable in any complex system. Python got rid of a number of those in the transition from Python 2 to Python 3; others might remain forever. Overall though I feel Python is more consistent than most other programming languages I come in contact with.
(2) Design decisions are not necessarily wrong when they don't match your mental model, or don't match what you know from other languages. Often there are different valid options, each with their own tradeoffs.
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