On 10Jul2019 20:30, Sarah Hembree <sarah12...@gmail.com> wrote:
How might I best make a linked list subscriptable? Below is skeleton code
for a linked list (my
actual is much more). I've done __iter__ and __next__ but I would like to
be able to do start:stop:stride I just can't figure out how. Suggestions or
just hints please?
Well, you could write a method to find and return element `n`, counting
from 0 (the root Node).
For start stop stride you could do the extremely simple approach:
iterate over a range() of the start stop stride and call the
get-element-n method. This will be very slow though (a complete scan for
every element).
Instead, you could write a method accepting a start, stop and stride.
Call the find-element-n method to get to start, lets call that `n`.
While n < stop, step forward `stride` elements and also bump `n` by
stride. That steps you along each element indicated by the
start:stop:stride.
You'll notice that this only works for a positive stride.
For a negative stride you're probably better off handing it to range(),
getting a list of values back from that as a list, and reversing the
list (which then has ascending values). Collect the elements indicated
by the list (because you can traverse the linkedlist forwards). Then
reverse the collected elements and return them.
Now, you _could_ accumulate each element in a list and return that at
the end. _Or_ you could make the function a generator and just yield
each element as found.
To turn all this into a subscriptable list, define the __getitem__
method as a function accepting an index. If that index is an int, just
return that element. If the index is a slice (start:stop:stride), call
the more complicated function to return multiple elements.
Cheers,
Cameron Simpson <c...@cskk.id.au>
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