How to sort sections of a list:-CodePudding

I’m trying to figure out how to sort a list but not all at once like in:

list.sort()

But instead I want to sort the first 3, then the next 3 and so on.

Let’s say my list is the following

list = [ F, V, T, O, D, Q, I, P, M]

Id want the out put to look like this:

[F, T, V, D, O, Q, I, M, P]

Does anyone know how I could go about doing this?

CodePudding user response：

You can sort a slice of a list, and use slice assignment to replace it in the original list:

>>> my_list = ['F', 'V', 'T', 'O', 'D', 'Q', 'I', 'P', 'M']
>>> for i in range(len(my_list) // 3):
...     my_list[i*3:i*3 3] = sorted(my_list[i*3:i*3 3])
...
>>> my_list
['F', 'T', 'V', 'D', 'O', 'Q', 'I', 'M', 'P']

Another option would be to build a whole new list with sum and just assign it to my_list at the end (whether or not this is equivalent depends on whether there are other references to my_list anywhere):

>>> my_list = ['F', 'V', 'T', 'O', 'D', 'Q', 'I', 'P', 'M']
>>> my_list = sum((sorted(my_list[i*3:i*3 3]) for i in range(len(my_list) // 3)), [])
>>> my_list
['F', 'T', 'V', 'D', 'O', 'Q', 'I', 'M', 'P']

CodePudding user response：

Just for fun a silly hack you shouldn't rely on:

i = iter(range(len(lst)))
lst.sort(key=lambda x: (next(i) // 3, x))

CodePudding user response：

my_list = ["F", "V", "T", "O", "D", "Q", "I", "P", "M"]

slice = 3

sorted_list = sum([sorted(my_list[i:i slice]) for i in range(0, len(my_list), slice)], [])

# ['F', 'T', 'V', 'D', 'O', 'Q', 'I', 'M', 'P']