How ro read mutli lined input into 2d arrays in python

Question

I\'ve been across a problem in python, the input format of the 2d array to be read is

3           # number of rows and columns of a square matrix
1 2 3       #          


        

Answer 1

If the numbers are separated by a single space your can use the following code:

n = int(input())
matrix = []
for i in range(n):
  row = [int(x) for x in input().split()]
  matrix.append(row)

If you have different separator then space you can put as argument in the split() function.

Answer 2

n = int(input())
matrix = dict()
for i in range(n):
    matrix["row"+str(i)] = input().split() # i assume you want the numbers seperated too

this take the number of lines input you want makes a dictionary with the number of inputs you initialy said

so matrix the dicitonary is now

{'row0': ['1', '2', '3', '4'], 
'row1': ['3', '4', '6', '9'], 
'row2': ['4', '6', '3', '1']}

incase you want them stored as intergers

n = int(input())
matrix = dict()
for i in range(n):
    matrix["row"+str(i)] = [int(i) for i in input().split()]

output

{'row0': [1, 2, 3, 4], 
'row1': [3, 4, 6, 9], 
'row2': [4, 6, 3, 1]}

or as a oneliner that just output list of lists

[[int(i) for i in input().split()] for _ in range(int(input()))]

output

[[1, 2, 3, 4], [3, 4, 6, 9], [4, 6, 3, 1]]

or as a dictionary oneliner

{'row'+str(q) : [int(i) for i in input().split()] for q in range(int(input()))}

output

{'row0': [1, 2, 3, 4], 'row1': [3, 4, 6, 9], 'row2': [4, 6, 3, 1]}

and as Patric pointed out a fast oneliner could be

{q : [int(i) for i in input().split()] for q in range(int(input()))}

output

{1: [1, 2, 3, 4], 2: [3, 4, 6, 9], 3: [4, 6, 3, 1]}

this solution is faster because dictionaries uses hashes, and thus dont have to loop through the whole list before getting to the desired index.