Question

I am fairly new to Python and I’m having trouble figuring out how to apply a list comprehension to part of a nested list (specifically at the index level).

For instance, if I have the following:

my_list = [[1,2], [3,7], [6,9], [4,3]]

new_list = [[i*2 for i in sublist] for sublist in my_list]

How would I alter my list comprehension to only apply the operation to index 1 of each sublist? I have experimented quite a bit with no success.

Answer 1

A more general version of mac’s:

>>> my_list = [[1,2], [3,7], [6,9], [4,3]]
>>> new_list = [[v*2 if i==0 else v for i,v in enumerate(sublist)] for sublist in my_list]
>>> new_list
[[2, 2], [6, 7], [12, 9], [8, 3]]