How can a Python list be sliced such that a column is moved to being a separate element column?

Question

I have a list of the following form:

[[0, 5.1, 3.5, 1.4, 0.2],
 [0, 4.9, 3.0, 1.4, 0.2],
 [0, 4.7, 3.2, 1.3, 0.2],
 [1, 4.6, 3.1, 1.5, 0.2],
 [1, 5.0, 3.6, 1.4, 0.2],
 [1, 5.4, 3.9, 1.7, 0.4],
 [1, 4.6, 3.4, 1.4, 0.3]]

I want to slice out the first column and add it as a new element to each row of data (so at each odd position in the list), changing it to the following form:

[[5.1, 3.5, 1.4, 0.2], [0],
 [4.9, 3.0, 1.4, 0.2], [0],
 [4.7, 3.2, 1.3, 0.2], [0],
 [4.6, 3.1, 1.5, 0.2], [1],
 [5.0, 3.6, 1.4, 0.2], [1],
 [5.4, 3.9, 1.7, 0.4], [1],
 [4.6, 3.4, 1.4, 0.3], [1],]

How could I do this?

So far, I have extracted the necessary information in the following ways:

targets = [element[0] for element in dataset]
features = dataset[1:]

Answer 1

Try indexing and then get flattened list- i used list comprehension for flattening.

>>>l=[[0, 5.1, 3.5, 1.4, 0.2],
 [0, 4.9, 3.0, 1.4, 0.2],
 [0, 4.7, 3.2, 1.3, 0.2],
 [1, 4.6, 3.1, 1.5, 0.2],
 [1, 5.0, 3.6, 1.4, 0.2],
 [1, 5.4, 3.9, 1.7, 0.4],
 [1, 4.6, 3.4, 1.4, 0.3]]
>>>[[i[1:],[i[0]]] for i in l]#get sliced list of lists
>>>[[[5.1, 3.5, 1.4, 0.2], [0]], [[4.9, 3.0, 1.4, 0.2], [0]], [[4.7, 3.2, 1.3, 0.2], [0]], [[4.6, 3.1, 1.5, 0.2], [1]], [[5.0, 3.6, 1.4, 0.2], [1]], [[5.4, 3.9, 1.7, 0.4], [1]], [[4.6, 3.4, 1.4, 0.3], [1]]]
>>>d=[[i[1:],[i[0]]] for i in l]
>>>[item for sublist in d for item in sublist]#flatten list d
>>>[[5.1, 3.5, 1.4, 0.2], [0], [4.9, 3.0, 1.4, 0.2], [0], [4.7, 3.2, 1.3, 0.2], [0], [4.6, 3.1, 1.5, 0.2], [1], [5.0, 3.6, 1.4, 0.2], [1], [5.4, 3.9, 1.7, 0.4], [1], [4.6, 3.4, 1.4, 0.3], [1]]

Just oneliner alternative-

[item for sublist in [[i[1:],[i[0]]] for i in l] for item in sublist] #Here l is that list

Answer 2

List comprehensions are nice but can be a bit hard to scan. Loops are still useful, especially when combined with extend:

res = []
for entry in dataset:
    res.extend([entry[1:], entry[:1]])

now:

import pprint    
pprint.pprint(res)

prints:

[[5.1, 3.5, 1.4, 0.2],
 [0],
 [4.9, 3.0, 1.4, 0.2],
 [0],
 [4.7, 3.2, 1.3, 0.2],
 [0],
 [4.6, 3.1, 1.5, 0.2],
 [1],
 [5.0, 3.6, 1.4, 0.2],
 [1],
 [5.4, 3.9, 1.7, 0.4],
 [1],
 [4.6, 3.4, 1.4, 0.3],
 [1]]