Extract specific columns from list

Question

I have a list that contain the column indexes as follows:

list1 = [0 ,2]

Another list of list would contain the file contents of a csv file as follows:

list2=[["abc", 1, "def"], ["ghi", 2, "wxy"]]

What can be the best way to create a new list that would only contain the values from list2 with the column numbers that are contained in list1 i.e.

newList = [["abc", "def"], ["ghi", "wxy"]]

I am having a hard time creating the sublists

Answer 1

You can use List Comprehension : -

newList = [[each_list[i] for i in list1] for each_list in list2]

Answer 2

If you are happy with a list of tuples, you can use operator.itemgetter

import operator
list1 = [0,2]
my_items = operator.itemgetter(*list1)
new_list = [ my_items(x) for x in list2 ]

(or you could use map here):

new_list = map(my_items, list2)

and as a 1 liner:

new_list = map(operator.itemgetter(*list1), list2)

operator.itemgetter probably has a slight performance advantage over nested list-comprehensions, but it's likely to be small enough that it's not worth worrying about.