对列表列表中的元素进行排序

Question

Hey I have a list that goes like:

List = [[[1,2],[4,5,3]],[[5,2],[3,4,7]],...]

and I want to sort the elements of each sublist, that the output looks like:

List = [[[2,1],[5,4,3]],[[5,2],[7,4,3]],...]

What I have already tried is creating a loop like this.

for i in List:
    for u in [i]:
        List[u].sort(reverse = True)
        print(List)

but it didnt worked. In other Blogposts I just found ways how to sort the lists, but not the elements in them. Thanks for your help

Answer 1

You may use a list comprehension, to easily retrieve the values, iterate over each sublist and sort the subsublist

values = [[[1, 2], [4, 5, 3]], [[5, 2], [3, 4, 7]]]
values = [[sorted(subsub, reverse=True) for subsub in sub] for sub in values]
print(values) # [[[2, 1], [5, 4, 3]], [[5, 2], [7, 4, 3]]]

Or with loops, you can just access the inner lists with the second loop and inline sort them

for sub in values:
    for subsub in sub:
        subsub.sort(reverse=True)

---

Note: use meaningful names to your variables

Answer 2

You are close, just a few things wrong:

for u in [i]: Do not wrap i in brackets. You are just creating a new list with i as its only element, and looping over that which is not what you want.

Second:

List[u].sort(reverse = True) You do not need to do List[u] , rather just u , because inside of this loop, u is equal to the sublist that you want to sort

Also a side note, variables should be lowercase

myList = [[[1,2],[4,5,3]],[[5,2],[3,4,7]]]
for i in myList: 
    for u in i: 
        u.sort(reverse=True) 
print(myList)

Answer 3

You are close with your approach although in your second loop you're enclosing i in a list which won't loop through each sub list and you only need to sort u as you're not going to slice a list with a list.

for i in List:
    for u in i:
        u.sort(reverse = True)

print(List)

Result:

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

PS If there could be only one layer of nesting then I'd suggest using isinstance to check before looping through and error-ing out due to attempting to sort an int

for i in List:
    if isinstance(i[0], list):
        for u in i:
            u.sort(reverse = True)
    else:
        i.sort(reverse = True)

Answer 4

Another approach using list comprehension (one liner):

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

li = [[sorted(i, reverse=True) for i in j] for j in li]

print(li)

Output:

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

Answer 5

Is this what you are looking for?

for i in List:
    for u in i:
        u.sort(reverse = True)

Answer 6

You can use Pandas to sort your data.

import pandas as pd

ist = [[[1,2],[4,5,3]],[[5,2],[3,4,7]]]
df = pd.DataFrame(ist)

I named the columns to read the columns easier.

df.columns = ['a', 'b']

Now we can sort the elements of the lists in each,

df['a'] = df.a.apply(lambda x: sorted(x,reverse=True))
df['b'] = df.b.apply(lambda x: sorted(x,reverse=True))

which yields,

print(df.head())

    a          b
0  [2, 1]  [5, 4, 3]
1  [5, 2]  [7, 4, 3]