Creating slice notation from string

[Bob van der Poel]

On Sep 2, 4:27 pm, Ethan Furman <et... at stoneleaf.us> wrote:
> Bob van der Poel wrote:
>
>
>
> >>For a one-liner:
>
> >>   x[slice(*map(int, x[1:-1].split(':')))]
>
> > Thanks.
>
> > Almost works :)
>
> > For s="[2]" and s="[1:2]" it's fine. But, if I have
>
> > s = "[:2]" then I get:
>
> >>>>x[slice(*[int(i) for i in s.strip("[]").split(":")])]
>
> > Traceback (most recent call last):
> >   File "<stdin>", line 1, in <module>
> > ValueError: invalid literal for int() with base 10: ''
>
> > Similar problem with  [2:].
>
> > Ideas?
>
> try:
>      start, end = s[1:-1].split(':')
> except ValueError:
>      start = int(s[1:-1] # only one value specified
>      end = start+1
> start = int(start) if start else 0
> end = int(end) if end else len(x)
> x[start:end]
>
> ~Ethan~

Yes ... I see. I'm thinking that eval() is looking very nice. If we do
it the above way we also have to check for empties using things like
[1::2] and I'm really getting confused about the possibilities :)