Print only the even numbers in nested lists

Question

This is what I have:

mylist1 = [[1,2,3], [4,5,6], [7,8,9]]   

for i in mylist1:
    if i[0] % 2 == 0:
        print(i[0])
    if i[1] % 2 == 0:
        print(i[1])
    if i[2] % 2 == 0:
        print(i[2])

Is there a shorter way?

Possible duplicate of [How to make a flat list out of list of lists](https://stackoverflow.com/questions/952914/how-to-make-a-flat-list-out-of-list-of-lists) ... and [Flattening a shallow list in Python (duplicate)](https://stackoverflow.com/questions/406121/flattening-a-shallow-list-in-python) — wwii, Jun 22 '19 at 03:19

APerson · Answer 1 · 2019-06-22T01:36:11.557

1

List comprehension?

print('\n'.join(str(i) for sublist in mylist1 for i in sublist if i % 2 == 0))

Less hardcore list comprehension?

for sublist in mylist1:
    print('\n'.join(i for i in sublist if i % 2 == 0))

For loop?

for sublist in mylist1:
    for i in sublist:
        if i % 2 == 0:
            print(i)

edited Jun 22 '19 at 01:36

answered Jun 22 '19 at 01:32

APerson

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Mark · Answer 2 · 2019-06-22T01:48:26.073

1

You can use filter with itertools' chain.from_iterable:

from itertools import chain
mylist1 = [[1,2,3], [4,5,6], [7,8,9]]   

print(list(filter(lambda x: x % 2 == 0, chain.from_iterable(mylist1))))

# [2, 4, 6, 8]

edited Jun 22 '19 at 01:48

answered Jun 22 '19 at 01:43

Mark

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1

That's elegant. – paisanco Jun 22 '19 at 01:47

score 0 · Accepted Answer · answered Jun 22 '19 at 01:34

0

You can use a nested loop try this.

mylist1 = [[1,2,3], [4,5,6], [7,8,9]]   

for i in mylist1:
    for j in i:
        if j % 2 == 0:
            print(j)

answered Jun 22 '19 at 01:34

Diego

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score 0 · Answer 4 · answered Jun 22 '19 at 01:37

0

If you know the format is going to be a list of lists, I suppose you could just use nested for loops

mylist1 = [[1,2,3], [4,5,6], [7,8,9]]  
for x in mylist1:
    for y in x:
        if y%2 == 0:
            print(y)

Unless you're asking it to be quicker in terms of CPU time in which case I would probably use numpy. Keep experimenting bud!

answered Jun 22 '19 at 01:37

Tclack88

21
5

Damn, looks like I was beat – Tclack88 Jun 22 '19 at 01:37

score 0 · Answer 5 · answered Jun 22 '19 at 02:12

0

You can just pass *param to chain :

from itertools import chain
[i for i in chain(*mylist1) if i % 2 == 0]

answered Jun 22 '19 at 02:12

LiuXiMin

1,225
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score 0 · Answer 6 · answered Jun 22 '19 at 03:24

Yet another option, a one-liner that uses no imports:

print(*[val for lst in mylist1 for val in filter(lambda x: x & 1 == 0, lst)])

Or if having them on separate lines is important:

print(*[val for lst in mylist1 for val in filter(lambda x: x & 1 == 0, lst)], sep = "\n")

Print only the even numbers in nested lists

6 Answers6