Python Indexing Multi-dimensional Arrays

Index represents the location number. The individual elements of a 2D array can be accessed by specifying the location number of the row and column of the element in the array as:

a[0][0] #represents 0th row and 0th column element in the array 'a'

b[1][3] #represents 1st row and 3rd column element in the array 'b'

Suppose 'a' is the array name. len(a) fun ction will give the number of rows in the array . a[0] represents the 0th row, a[1] represents the 1st row, etc. So, in general, a[i] represents the ith row elements. Hence, to display only rows of the 2D array, we can write:

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for i in range(len(a)):
   print(a[i])

Each row may contain some columns which represent the elements. To know, how many elements are there in a row, we can use len(a[i]) . Here, if i = 0, then len(a[0]) represents the number of columns in 0th row. Similarly if i=1, then len(a[1]) represents the number of columns in 1st row and so on. In this way, len(a[i]) represents the number of columns in ith row. So, the following loops will access all elements from the 2D array:

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for i in range(len(a)): 
    for j in range(len(a[i])): 
          print(a[i][j], end='  ')
print()

Python Indexing Multi-dimensional Arrays

A Python program to retrieve the elements from a 2D array and display them using for loops.

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from numpy import * 
a = array([[1,2,3], [4,5,6], [7,8,9]])
for i in range(len(a)):  
  print(a[i])
for i in range(len(a)): 
   for j in range(len(a[i])): 
     print(a[i][j], end='')

A Python program to retrieve the elements from a 3D array.

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from numpy import * 
a = array([[[1,2,3], [4,5,6]], [[7,8,9], [10,11,12]]])
for i in range(len(a)): 
  for j in range(len(a[i])): 
for k in range(len(a[i][j])): 
        print(a[i][j][k], end='\t') 
print() 
print()