How to print a 2D array in a "pretty" format?

Question

Hello so let's say I have a 2D array a = [[1,2,1,2], [3,4,5,3], [8,9,4,3]] and I would like to print this out in a grid like table. So far the code I have is:

def printArray(a):
    for row in range(len(a[0])):
        for col in range (len(a[0])):
            b = print("{:8.3f}".format(a[row][col]), end = " ")
        print(b)

When this is printed out it gives me:

  1.000    2.000    1.000    2.000 None
  3.000    4.000    5.000    3.000 None
  8.000    9.000    4.000    3.000 None

And then the error:

File "hw8pr2.py", line 17, in printArray
b = print("{:8.3f}".format(a[row][col]), end = " ")

IndexError: list index out of range

Can someone tell me why this is happening? I don't want the 'None' at the end of each row either. I want it to output:

  1.000    2.000    1.000    2.000
  3.000    4.000    5.000    3.000
  8.000    9.000    4.000    3.000

Answer 1

Here is what your are using:

def printArray(a):
    for row in range(len(a[0])):
        for col in range (len(a[0])):
            b = print("{:8.3f}".format(a[row][col]), end = " ")
        print(b)

You are using two for loops with len(a[0]) but your input data isn't a square, so that can't work!

You might consider using this:

def printA(a):
    for row in a:
        for col in row:
            print("{:8.3f}".format(col), end=" ")
        print("")

That will give you this:

In [14]: a = [[1, 2, 1, 2], [3, 4, 5, 3], [8, 9, 4, 3]]

In [15]: printA(a)
   1.000    2.000    1.000    2.000 
   3.000    4.000    5.000    3.000 
   8.000    9.000    4.000    3.000 

In [16]: b = [[1, 2, 1, 2, 5], [3, 4, 7, 5, 3], [8, 2, 9, 4, 3], [2, 8, 4, 7, 6]]

In [17]: printA(b)
   1.000    2.000    1.000    2.000    5.000 
   3.000    4.000    7.000    5.000    3.000 
   8.000    2.000    9.000    4.000    3.000 
   2.000    8.000    4.000    7.000    6.000