Python: 2D arrays

Python does not have true multi-dimension arrays, but structures can be built to hold 2D

Here are a few different ways of creating 2D arrays:

Two ways to create a 2D array

# empty matrix matrix = [] print(matrix) # creates a 10 row by 5 column array for row in range(10): # append a new row to the matrix matrix.append([]) for col in range(5): #append a new element to the current row matrix[row].append(row * 10 + col) # matrix = [[0 for i in xrange(5)] for i in xrange(5)]

This will do the same as the above

matrix = [[+col + row * 10 for col in range(5)] for row in range(10)]

Printing 2D arrays

# print the matrix one row at a time # will print an extra empty list [] print ("print one row at a time") for r in matrix: print(r) # print a row at a time print ("another way to print one row at a time") for r in range(10): print(matrix[r]) # print an element at a time print ("one element at a time") for r in range(10): for c in range(5): print(matrix[r][c]) # print the element from row 6, col 2 print ("the element from row 6 col 2") print(matrix[6][2]) print ("the matrix") print(matrix)

print ("ways to print row 2") print(matrix[2][:3]) print(matrix[2])

print ("print rows 1 and 2") print(matrix[1:3]) print() print (column(matrix,0)) matrix = [[+col + row * 10 for col in range(3)] for row in range(5)] print(matrix) m = [] m.append(matrix[2] for c in range(1)) #print(m)

Extract column from a matrix

def column(matrix, i): return [row[i] for row in matrix]