On 2019-04-03 09:38, Stephen J. Turnbull wrote:
> MRAB writes:
> > On 2019-04-02 19:10, Stephen J. Turnbull wrote:
>
> > > word[len(prefix) if word.startswith(prefix) else 0:]
>
> > It could be 'improved' more to:
> >
> > word[word.startswith(prefix) and len(prefix) : ]
>
> Except that it would be asymmetric with suffix. That probably doesn't
> matter given the sequence[:-0] bug.
>
> BTW thank you for pointing out that bug (and not quoting the code
> where I deliberately explicitly introduced the null suffix! ;-) This
> works:
>
> word[:-len(suffix) or len(word)] if word.endswith(suffix) else word
>
I would've written it as:
word[: len(word) - len (suffix)] if word.endswith(suffix) else word
> Do tutorials mention this pitfall with computed indicies (that -0 is
> treated as "beginning of sequence")? (I should check myself, but
> can't spend time this week and so probably won't. :-( )
>
> > > prefix. So that's the one I'd go with, as I can't think of any
> > > applications where multiple copies of the same string would be
useful.
>
> > _Neither_ version copies if the word doesn't start with the prefix. If
> > you won't believe me, test them! :-)
>
> Oh, I believe you. It just means somebody long ago thought more
> deeply about the need for copying immutable objects than I ever have.
>
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