To understand this example, you should have the knowledge of following Python programming topics:
In Python, we can implement a matrix as nested list (list inside a list). We can treat each element as a row of the matrix.
X = [[1, 2], [4, 5], [3, 6]] would represent a 3x2 matrix. First row can be selected as
X and the element in first row, first column can be selected as
We can perform matrix addition in various ways in Python. Here are a couple of them.
# Program to add two matrices using nested loop X = [[12,7,3], [4 ,5,6], [7 ,8,9]] Y = [[5,8,1], [6,7,3], [4,5,9]] result = [[0,0,0], [0,0,0], [0,0,0]] # iterate through rows for i in range(len(X)): # iterate through columns for j in range(len(X)): result[i][j] = X[i][j] + Y[i][j] for r in result: print(r)
[17, 15, 4] [10, 12, 9] [11, 13, 18]
In this program we have used nested
for loops to iterate through each row and each column. At each point we add the corresponding elements in the two matrices and store it in the result.
# Program to add two matrices # using list comprehension X = [[12,7,3], [4 ,5,6], [7 ,8,9]] Y = [[5,8,1], [6,7,3], [4,5,9]] result = [[X[i][j] + Y[i][j] for j in range(len(X))] for i in range(len(X))] for r in result: print(r)
The output of this program is the same as above. We have used nested list comprehension to iterate through each element in the matrix.
List comprehension allows us to write concise codes and we must try to use them frequently in Python. They are very helpful.