How to convert list to list of list for adjacent numbers

user_15299206 0
Viewed 38
  • i have list [31, 32,33, 1,2,3,4, 11,12,13,14]
  • I need to put into adjacent numbers into one list for i, i+1

Expected out [[1,2,3,4], [11,12,13,14], [31, 32,33]]

l = [31, 32,33, 1,2,3,4, 11,12,13,14]
l.sort() #sorted the items
new_l = []
for i in l:
    temp_l = []  # temp list before appending to main list
    if i + 1 in l: # if i + 1 is present append to temp_list
        temp_l.append(i)
    new_l.append(temp_l) # temp_l has to append to main list

My out is wrong : [[1], [2], [3], [], [11], [12], [13], [], [31], [32], []]

list python
3 Answers

You can use itertools.groupby:

from itertools import groupby

l = [31, 32, 33, 1, 2, 3, 4, 11, 12, 13, 14]
l.sort() 

out = [
    list(v for _, v in g)
    for _, g in groupby(enumerate(l), key=lambda v: v[0] - v[1])
]
print(out)

Prints:

[[1, 2, 3, 4], [11, 12, 13, 14], [31, 32, 33]]

Without itertools.groupby:

l = [31, 32, 33, 1, 2, 3, 4, 11, 12, 13, 14]
l.sort()

out = [[l[0]]]
for i in range(1, len(l)):
    if l[i] - out[-1][-1] == 1:
        out[-1].append(l[i])
    else:
        out.append([l[i]])

print(out)

Edit: Added .sort()

user_100359850

Use a for loop, enumerate() and sort()

l = [31, 32, 33, 1, 2, 3, 4, 11 ,12, 13, 14]
# sort list
l = sorted(l)

sub_l = []
new_list = []
for i, num in enumerate(l):
    # check if not last element
    if not (i + 1) == len(l):
        # check if next element is the same as the current + 1
        if num + 1 == l[i+1]:
            sub_l.append(num)
        else:
            # append sub-list to parent-list and reset sub-list
            new_list.append(sub_l)
            sub_l = []

print(new_list)

Output

[[1, 2, 3], [11, 12, 13], [31, 32]]
user_135080450

You can append an empty sub-list to the output list when the difference between the current number and the last number in the last sub-list in the output list is not 1, and keep appending the current number to the last sub-list of the output list:

l = [31, 32,33, 1,2,3,4, 11,12,13,14]
l.sort()

output = []
for i in l:
    if not output or i - output[-1][-1] != 1:
        output.append([])
    output[-1].append(i)

output becomes:

[[1, 2, 3, 4], [11, 12, 13, 14], [31, 32, 33]]

Demo: https://replit.com/@blhsing/UnimportantValidTelecommunications

user_68909120
Related