CODEWITHSUNDEEP
pythonmultidimensional-arraylist-comprehension
Brent Gunderson
Brent Gunderson

Reputation: 303

Python: changing shape of list of lists

Using python, I'd like to convert this list of lists:

list_3_5 = [[1,2,3,4,5],[6,7,8,9,10],[11,12,13,14,15]]

To a different shape -- a list of 6 lists, where the first 3 new lists have the first three values from the each of the 3 main lists in list_3_5, and then the last 3 new lists have the remaining values from list_3_5:

[[1,2,3],[6,7,8],[11,12,13],[4,5],[9,10],[14,15]]

Any help appreciated.

Updates:

For longer lists, this:

list2 = [list(range(1, 34)), list(range(34, 67)), list(range(67, 100))]

list2b = [list2[i][:5] for i in range(0, len(list2))] + [
    list2[i][5:] for i in range(0, len(list2))
]

or this

list2 = [list(range(1, 34)), list(range(34, 67)), list(range(67, 100))]
list2b = list(range(2 * len(list2)))

for key, element in enumerate(list2):
    list2b[key] = element[:5]
    list2b[key + len(list2)] = element[5:]

Gives this (modifies my original list of 3 lists each with 33 elements, into a list of 6 lists, the first three lists each having 5 elements, and the last three each having 28) :

[[1, 2, 3, 4, 5],
 [34, 35, 36, 37, 38],
 [67, 68, 69, 70, 71],
 [6, 7, 8, ..., 33], 
 [39, 40, 41, ..., 66],
 [72, 73, 74, ... 99]]

But what I would like is this (for this example, a list of 19 lists with 5 elements each, and 1 list at the end with remaining 4 elements):

[[1, 2, 3, 4, 5], 
 [6, 7, 8, 9, 10],
 [11, 12, 13, 14, 15],
 [16, 17, 18, 19, 20],
 ....
 ....
 [91, 92, 93, 94, 95],
 [96, 97, 98, 99]]

seems like this, but I can't quite see how to modify for my case: reshape an irregular list in python

Upvotes: 0

Views: 1000

Answers (3)

MECoskun
MECoskun

Reputation: 909

Here is a solution with double for loops that will work for an arbitrary length list:

list_3_5 = [[1,2,3,4,5],[6,7,8,9,10],[11,12,13,14,15]]
newlist = []

for element in list_3_5:
    newlist.append(element[:3])

for element in list_3_5:
    newlist.append(element[3:])    

newlist

Out: [[1, 2, 3], [6, 7, 8], [11, 12, 13], [4, 5], [9, 10], [14, 15]]

But wait! There is more:

list_3_5 = [[1,2,3,4,5],[6,7,8,9,10],[11,12,13,14,15]]
newlist = list(range(2*len(list_3_5)))

for key, element in enumerate(list_3_5):
    newlist[key] = element[:3]
    newlist[key+len(list_3_5)] = element[3:]

newlist
[[1, 2, 3], [6, 7, 8], [11, 12, 13], [4, 5], [9, 10], [14, 15]]

Below part answers the updated section of the question:

biglist = []
for i in list2:
    biglist = biglist + i
#Here we put all small lists in the given list into a big list
print(biglist)

#construct an empty list to save the result as we go:
newlist = []

#add sections of 5 to newlist
while len(biglist) >= 5:
    newlist.append(biglist[:5])
    biglist = biglist[5:]

#add the remaining part of biglist to the newlist:
newlist.append(biglist)
print(newlist)

Output is:

[[1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, 13, 14, 15], [16, 17, 18, 19, 20], [21, 22, 23, 24, 25], [26, 27, 28, 29, 30], [31, 32, 33, 34, 35], [36, 37, 38, 39, 40], [41, 42, 43, 44, 45], [46, 47, 48, 49, 50], [51, 52, 53, 54, 55], [56, 57, 58, 59, 60], [61, 62, 63, 64, 65], [66, 67, 68, 69, 70], [71, 72, 73, 74, 75], [76, 77, 78, 79, 80], [81, 82, 83, 84, 85], [86, 87, 88, 89, 90], [91, 92, 93, 94, 95], [96, 97, 98, 99]]

Upvotes: 1

Nastaran Khalili
Nastaran Khalili

Reputation: 56

If you want to have a general code to separate first three elements, try this:

new_list=[list_3_5[i][:3] for i in range(0,len(list_3_5))]+[ list_3_5[i][3:] for i in range(0,len(list_3_5))]

Upvotes: 1

IoaTzimas
IoaTzimas

Reputation: 10624

Try this:

[list_3_5[0][:3],list_3_5[1][:3], list_3_5[2][:3], list_3_5[0][3:],list_3_5[1][3:], list_3_5[2][3:]]

Output:

[[1, 2, 3], [6, 7, 8], [11, 12, 13], [4, 5], [9, 10], [14, 15]]

Upvotes: 0

Related Questions