Separating sublist into multiple list and assigning dynamic list_name

Question

I am trying to split a nested list into multiple lists and assign their name dynamically. Untill now, I tried the code below, but it only works when we have equal length sublists and we give them names manually.

sub_list = [[1,2,3],[4,5,5],   [2,63,6]]

l1, l2, l3 = map(list, zip(*sub_list))
print(l1)
print(l2)
print(l3)

# Output
[1, 4, 2]
[2, 5, 63]
[3, 5, 6]

The approach above will fail when we have unequal length sublists such as (sub_list = [[1,2,3],[4,5], [2]]) and it does not give lists dynamic names.

I know it can be done by for loop, but I am not able to make list_name using a loop.

Any help will help me to reach more closure to my work

What output do you expet for `sub_list = [[1,2,3],[4,5], [2]]`? — Manuel, May 13 '19 at 19:53

score 0 · Answer 1 · answered May 13 '19 at 19:55

you could use zip_longest from itertools as follows:

sub_list = [[1,2,3],[4,5], [2]]
from itertools import zip_longest
l1, l2, l3 = map(list, zip_longest(*sub_list))
print(l1)
print(l2)
print(l3)

Output:  
# [1, 4, 2]
# [2, 5, None]
# [3, None, None]

score 0 · Answer 2 · answered May 13 '19 at 19:58

Answering the first question: If you don't want to give a manual name assing the map() to just one variable:

sub_list = [[1,2,3],[4,5,5],   [2,63,6]]

rotated = map(list, zip(*sub_list))

for r in rotated:
    print(r)

# Output
# [1, 4, 2]
# [2, 5, 63]
# [3, 5, 6]

score 0 · Answer 3 · answered May 13 '19 at 19:59

Not completely sure what you want to accomplish, but I suggest you take a look at:

How to use itertools.zip_longest(): Python: zip-like function that pads to longest length? (You can filter out the Nones afterwards)
How to create dynamically named vars (although this is generally not the best thing to do): How do I create a variable number of variables?

score 0 · Answer 4 · answered May 13 '19 at 20:30

The following code performs in both of your special cases:

There are no errors if some input lists are shorter than others

Names are procedurally/dynamically generated

def rotate_list_matrix(rows):
    nrows = len(rows)

    col_counts = map(lambda lyst: len(lyst), rows)
    ncols = max(col_counts)

    for ci in range(0, ncols): # column index
        lyst = list()
        list_name = "l" + str(ci + 1)
        globals()[list_name] = lyst
        for ri in range(0, nrows):
            try:
                lyst.append(rows[ri][ci])
            except:
                break
    return


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

list_matb = [[1, 2, 3],
             [4, 5   ],
             [7      ]]

rotate_list_matrix(list_matb)

print(l1)
print(l2)
print(l3)

Separating sublist into multiple list and assigning dynamic list_name

4 Answers4