Flattening a 2d list into 1d list in python-CodePudding

I have a list of 2D elements

m = [[1,2,3,4,5],[6,7,8,9,10],[11,12,13,14,15],[16,17,18,19,20]]

and I want my output to be:

I tried this loop:

for i in range(3):
    for k in range(i,len(m),3):
        print(*m[i][k:k 3],sep='\t')

but it prints

and gives me an error

I'm not sure if it is possible since it is going on the next element. Can anyone help me on this?

CodePudding user response：

You can use this snippet

m = [[1,2,3,4,5],[6,7,8,9,10],[11,12,13,14,15],[16,17,18,19,20]]

flag=0

for i in range(len(m)):

for j in range(len(m[i])):
    if(flag==3):
        print()
        flag=0
    print(m[i][j],end=" ")
    flag =1

I think it may work out Thanks !!!

CodePudding user response：

An approach like this would work:

m = [[1,2,3,4,5],[6,7,8,9,10],[11,12,13,14,15],[16,17,18,19,20]]

curr = 0
for i in m:
  for j in i:
    curr  = 1
    if(curr % 3 == 0):
      print(j)
    else:
      print(j, end = ' ')

Output:

You can create a variable, curr, to act as a counter variable. Then, iterate through every element of m, and increment curr with each iteration. For every third element, given by curr % 3 == 0%, we print an element WITH a newline. For every not-third element, we print the element without a newline.

I hope this helped! Please let me know if you have any further questions or clarifications :)

CodePudding user response：

import itertools
x = list(itertools.chain(*m))
print([x[i:i 3] for i in range(0,len(x),3)])

Of course, the above will print the whole thing as a list of lists, but you can go from there to printing each of the individual sublists.

CodePudding user response：

one-line version:

print("".join([str(e) " " if e%3!=0 else str(e) "\n" for row in m for e in row]))

P.S. m = [[1,2,3,4,5],[6,7,8,9,10],[11,12,13,14,15],[16,17,18,19,20]] as that of OP.

easy-to-read version:

m does not need to be identical to that of OP. Could be any 2d matrix.

flat = [e for row in m for e in row]
for i in range(len(flat)):
    if i%3 != 2 : print(flat[i], end = " ")
    else : print(flat[i], end = "\n")
if len(flat)%3 != 0: print("")

CodePudding user response：

I would try something like

count = 0
for arr in matrix:
    for num in arr:
        print(num, end=' ')
        count  = 1
        if count == 3:
            print()
            count = 0

CodePudding user response：

itertools.chain will effectively combine all the sublists into one, and more_itertools.chunked will break it up into equal-sized segments.

The asterisks are for unpacking; in this case print(*triplet) is effectively the same as print(triplet[0], triplet[1], triplet[2]), and print automatically inserts a space between multiple arguments by default.

from itertools import chain
from more_itertools import chunked

m = [[1,2,3,4,5], [6,7,8,9,10], [11,12,13,14,15], [16,17,18,19,20]]

for triplet in chunked(chain(*m), 3):
    print(*triplet)