Turning a list into nested lists in python

Question

Possible Duplicate:
How can I turn a list into an array in python?

How can I turn a list such as:

<         


        

Answer 1

This assumes that data_list has a length that is a multiple of three

i=0
new_list=[]
while i<len(data_list):
  new_list.append(data_list[i:i+3])
  i+=3

Answer 2

I hope this will be helpful to you. It converts a list into a list of lists

list1= [ i for i in range(0,8+1] nested =[] for i in list1: if len(nested) !=0: if i %3!=0: nested.append([i]) else: nested[len(nested)-1].append(i) else: nested.append([i]) print(nested

Answer 3

Do you have any sort of selection criteria from your original list?

Python does allow you to do this:

new_list = []
new_list.append(data_list[:3])
new_list.append(data_list[3:6])
new_list.append(data_list[6:])

print new_list
# Output:  [ [0,1,2] , [3,4,5] , [6,7,8] ]

Answer 4

This groups each 3 elements in the order they appear:

new_list = [data_list[i:i+3] for i in range(0, len(data_list), 3)]

Give us a better example if it is not what you want.

Answer 5

Something like:

map (lambda x: data_list[3*x:(x+1)*3], range (3))

Answer 6

The following function expands the original context to include any desired list of lists structure:

def gen_list_of_lists(original_list, new_structure):
    assert len(original_list) == sum(new_structure), \
    "The number of elements in the original list and desired structure don't match"
        
    list_of_lists = [[original_list[i + sum(new_structure[:j])] for i in range(new_structure[j])] \
                     for j in range(len(new_structure))]
        
    return list_of_lists

Using the above:

data_list = [0,1,2,3,4,5,6,7,8]
    
new_list = gen_list_of_lists(original_list=data_list, new_structure=[3,3,3])
# The original desired outcome of [[0,1,2], [3,4,5], [6,7,8]]

new_list = gen_list_of_lists(original_list=data_list, new_structure=[2,3,3,1])
# [[0, 1], [2, 3, 4], [5, 6, 7], [8]]