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comp / comp.lang.python / Re: Two python issues

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o Re: Two python issuesdn

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Subject: Re: Two python issues
From: dn
Newsgroups: comp.lang.python
Organization: DWM
Date: Tue, 5 Nov 2024 21:41 UTC
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Subject: Re: Two python issues
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On 6/11/24 10:08, Jason Friedman via Python-list wrote:
>>
>> (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!).
>>
>
> I'm not sure if this answers your objection but the note in the
> documentation (https://docs.python.org/3/library/stdtypes.html#str.find)
> says:
>
> The find() method should be used only if you need to know the position of
> sub.
>
> I think the use case above is a little bit different.

Not really, there are two questions:

1. is x in sequence (or in this case "not in")
2. where is x within sequence (find())

There are situations where one might be used, similarly where the other
will be used, and still more where both apply.

That said, and with @Cameron's observation, the idea that a function's
return-value (appears to) performs two functionalities is regarded as a
'code-smell' in today's world - either it indicates "found" or it
indicates "where found" (see also various APIs which return both a
boolean: success/fail, and a value: None/valid-info).

The problem with the third scenario being that purity suggests we should
use both (1) and (2) which seems like duplication - and is certainly
going to take more CPU time.
(will such be noticeable in your use-case?)

Backward-compatibility... ('nuff said!)

With reference to the OP content about slicing:
- Python's memory-addressing is different from many other languages.
Thus, requires study before comparison/criticism
- there are major differences in what can be accomplished with mutable
and immutable objects

--
Regards,
=dn

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