Multidimensional Array By User Input In Python

I used Jupyter notebook, I am new to Python, I try to fetch value from user in multidimensional array how I do that? I write a little code, after put first value I get error that I

Solution 1:

I took @Austin great answer and made some little changes:

import numpy as np

n_rows = int(input("Enter number of rows: "))
n_cols = int(input("Enter number of columns: "))

arr = [[int(input("Enter value for {}. row and {}. column: ".format(r + 1, c + 1))) for c inrange(n_cols)] for r inrange(n_rows)]

print(np.array(arr))

The output is:

Enter number ofrows: 2
Enter number of columns: 3
Enter valuefor1.rowand1.column: 1
Enter valuefor1.rowand2.column: 2
Enter valuefor1.rowand3.column: 3
Enter valuefor2.rowand1.column: 4
Enter valuefor2.rowand2.column: 5
Enter valuefor2.rowand3.column: 6
[[123]
 [456]]

You got an exception, because you initialized an empty array and used invalid indices. With this answer you generate the array after you have entered the users input.

---

Here is the long version of the one-liner (arr = [[...) which gives you the same result:

outer_arr = []
for r in range(n_rows):
    inner_arr = []
    for c in range(n_cols):
        num = int(input("Enter value for {}. row and {}. column: ".format(r + 1, c + 1)))
        inner_arr.append(num)
    outer_arr.append(inner_arr)

print(np.array(outer_arr))

Solution 2:

You can use a list-comprehension here as the final result is a list of lists:

lengthrow = int(input("enter array row length: "))
lengthcol = int(input("enter array col length: "))

arr = [[int(input("enter value: ")) for _ inrange(lengthcol)] for _ inrange(lengthrow)]

print(arr)

Problem with your code:

arr = array([[],[]])
print(arr.shape)
# (2, 0)

That means you have a size 0 column in array, so when you do arr[0][0], for example, it throws error.

Solution 3:

The problem is the shape of the initial array:

In [1]: arr = np.array([[], []])
In [2]: arr
Out[2]: array([], shape=(2, 0), dtype=float64)
In [3]: arr[0]
Out[3]: array([], dtype=float64)
In [4]: arr[0][0]
... 
IndexError: index 0isoutof bounds for axis 0with size 0

Think of this array as 2 rows, 0 columns. You can't reference a non-existent column. And, in contrast to some other languages, you can't grow an array simply by referencing a new index. Once created the size is fixed.

While others have shown nice list comprehension approaches, I'll show how to use your approach correctly:

In [8]: lengthrow, lengthcol = 2,3    # or user input
In [9]: arr = np.zeros((lengthrow, lengthcol), dtype=int)  # large enough array
In [10]: arr
Out[10]: 
array([[0, 0, 0],
       [0, 0, 0]])
In [11]: for i in range(2):
    ...:     for j in range(3):
    ...:         arr[i,j] = int(input(f'{i},{j}:'))
    ...:         
0,0:00,1:10,2:21,0:31,1:41,2:5
In [12]: arr
Out[12]: 
array([[0, 1, 2],
       [3, 4, 5]])