Complex list slice/index in python

Question

I have a list that looks like this:

lst = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]

I'd like to generate a filtered list that looks like this:

filtered_lst = [2, 6, 7, 9, 10, 13]

Does Python provide a convention for custom slicing. Something such as:

lst[1, 5, 6, 8, 9, 12] # slice a list by index

Answer 1

Use operator.itemgetter():

from operator import itemgetter

itemgetter(1, 5, 6, 8, 9, 12)(lst)

Demo:

>>> from operator import itemgetter
>>> lst = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]
>>> itemgetter(1, 5, 6, 8, 9, 12)(lst)
(2, 6, 7, 9, 10, 13)

This returns a tuple; cast to a list with list(itemgetter(...)(lst)) if a that is a requirement.

Note that this is the equivalent of a slice expression (lst[start:stop]) with a set of indices instead of a range; it can not be used as a left-hand-side slice assignment (lst[start:stop] = some_iterable).

Answer 2

Numpy arrays have this kind of slicing syntax:

In [45]: import numpy as np

In [46]: lst = np.array([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13])

In [47]: lst[[1, 5, 6, 8, 9, 12]]
Out[47]: array([ 2,  6,  7,  9, 10, 13])