Taking user input of 2-D array in a given format

Question

I have a 2-D 6x6 array, A. I want its values to be input by the user in the following format or example:

0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0

where the 0's indicate the places where the user would write their values.

This is my code. It returns an error in split().

def arr_input(x):
    for i in range(6):
         for j in range(6):
              n = int(input().split(' '))
              if n>=-9 and n<=9:
                   x[i][j] = n
    print "\n"

I don't want input in a single line. Please help!

EDIT 1 The code I needed was already provided :D. Nevertheless, I learned something new and helpful. Here is the existing code to do the task I wanted:

arr = []
for arr_i in xrange(6):
    arr_temp = map(int,raw_input().strip().split(' '))
    arr.append(arr_temp)

`split` returns a list. Argument to int() must be string or a number. The error message would have conveyed this. Please post the error message too. — gaganso, Jun 09 '16 at 18:24
Possible duplicate of [How to input matrix (2D list) in Python?](https://stackoverflow.com/questions/22741030/how-to-input-matrix-2d-list-in-python) — Georgy, Jul 12 '19 at 09:24

score 1 · Accepted Answer · edited Jun 09 '16 at 19:28

First of all, you are using input() which returns int when you enter numbers in terminal. You should use raw_input() and get it line by line.

Second, you are trying to convert a list to integer, you should loop through the list values, convert and insert on the resulting list.

Fixed code:

def arr_input(x):
    for i in range(6):
        num_list = raw_input().split(' ')
        for j, str_num in enumerate(num_list):
            n = int(str_num)
            if n >= -9 and n <= 9:
                x[i][j] = n
    print "\n"

Here, I used enumerate() to loop though the number list by getting its index each iteration.

Sam · Answer 2 · 2016-06-09T20:09:46.680

There's an inconsistency in how you're treating the input. In python 2.7, the input() function is designed to read one, and only one, argument from stdin.

I'm not exactly sure which way you're trying to read the input in. The nested for loop suggests that you're trying to read the values in one by one, but the split suggests that you're doing it line by line. To cover all bases, I'll explain both cases. At least one of them will be relevant.

Case 1: Let's say you've been inputting the values one by one, i.e.

1
4
9
4
...

In this case, what's happening is that the input() function is automatically parsing the inputs as integers, and when you try running split() on an integer there's a type error. Python is expecting a string and you're providing an int. That's going to break. There's an easy solution--this can be fixed by simply replacing that line with

n = input()

Case 2: Let's say you're inputing the numbers line by line, as strings. By this, I mean something like:

"1 3 4 5 7 9"
"4 1 8 2 5 1"
...

What's occurring here is that int(...) is trying to cast a list of strings into an integer. That will clearly break the code. A possible solution would be to restructure the code by gett rid of the inner for loop. Something like this should work:

def arr_input(arr):
    for i in range(6):
        s = input()
        nums_s = s.split(' ')
        nums = [int(x) for x in nums_s]
        arr.append(nums)
    print "\n"
    return arr

# Usage
a = []
print(a)
a = arr_input(a)
print(a)

Tonechas · Answer 3 · 2016-06-10T11:24:28.777

Give this one-liner a try:

def arr_input(N=6):
    print 'Enter %d by %d array, one row per line (elements separated by blanks)' % (N, N)    
    return [[n if abs(n)<=9 else 0 for n in map(int, raw_input().split())] for i in range(N)]

The following interactive session demonstrates its usage:

>>> A = arr_input(3)
Enter 3 by 3 array, one row per line (elements separated by blanks)
1 2 -3
4 5 -6
8 9 10
>>> A
[[1, 2, -3], [4, 5, -6], [8, 9, 0]]

Taking user input of 2-D array in a given format

3 Answers3