How to create nested loop in python?

Question

In python I'm trying to write nested loops in one line. I've seen a lot of examples, but in all of them the inner iterable variable is different compared to the outer one. So in my case, it won't work. Here's my try:

my_list = [for ip in subnet for subnet in subnets]

where I'm getting:

Unresolved reference 'subnet'

checkout https://stackoverflow.com/questions/24591917/nested-loop-python — YUVI_1303, Nov 10 '22 at 16:53

cmauck10 · Accepted Answer · 2022-11-10T21:46:33.567

1

There is a syntax error, it should be

my_list = [ip for subnet in subnets for ip in subnet]

edited Nov 10 '22 at 21:46

answered Nov 10 '22 at 16:59

cmauck10

163
3

didn't work in this case: `[pool.apply_async(handle_ip, (ip,)) for ip in subnet for subnet in subnets]` – Algo Nov 10 '22 at 17:03
It's unintuitive, but you have to flip the loop conditions to ensure that the loop variables are declared in the proper order. `[pool.apply_async(handle_ip, (ip,)) for subnet in subnets for ip in subnet]` – 0x5453 Nov 10 '22 at 17:05
You're 100% right, edited answer above. – cmauck10 Nov 10 '22 at 17:07

Ljg · Answer 2 · 2022-11-11T07:59:31.030

-1

Try with this

my_list = [[ip for ip in subnet] for subnet in subnets]

is a way to nest loops in list comprehension

Can check this too https://www.geeksforgeeks.org/nested-list-comprehensions-in-python/

edited Nov 11 '22 at 07:59

answered Nov 10 '22 at 17:00

Ljg

141
8

That inner comprehension should be `[ip for ip in subnet]`. It doesn't make sense to start a list comprehension with `for`. – 0x5453 Nov 10 '22 at 17:04
this *doesn't even compile* – juanpa.arrivillaga Nov 10 '22 at 17:37
@0x5453 sorry my mistake, i forgot to put ip at the start. I'm going to edit it. – Ljg Nov 11 '22 at 07:56

How to create nested loop in python?

2 Answers2