In Python list comprehension is it possible to access the item index?

Question

Consider the following Python code with which I add in a new list2 all the items with indices from 1 to 3 of list1:

for ind, obj in enum         


        

Answer 1

Unless your real use case is more complicated, you should just use a list slice as suggested by @wim

>>> list1 = ['zero', 'one', 'two', 'three', 'four', 'five', 'six']
>>> [x for ind, x in enumerate(list1) if 4 > ind > 0]
['one', 'two', 'three']
>>> list1[1:4]
['one', 'two', 'three']

For more complicated cases - if you don't actually need the index - it's clearer to iterate over a slice or an islice

list2 = [x*2 for x in list1[1:4]]

or

from itertools import islice
list2 = [x*2 for x in islice(list1, 1, 4)]

For small slices, the simple list1[1:4]. If the slices can get quite large it may be better to use an islice to avoid copying the memory

Answer 2

If you use enumerate, you do have access to the index:

list2 = [x for ind, x in enumerate(list1) if 4>ind>0]

Answer 3

list2 = [x for ind, x in enumerate(list1) if 4 > ind > 0]