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Book4_Ch06_Python_Codes/Bk4_Ch6_01.py

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+
+###############
+# Authored by Weisheng Jiang
+# Book 4  |  From Basic Arithmetic to Machine Learning
+# Published and copyrighted by Tsinghua University Press
+# Beijing, China, 2022
+###############
+
+
+# Bk4_Ch6_01.py
+
+import numpy as np
+
+A = np.array([[1, 2, 3, 0,  0],
+              [4, 5, 6, 0,  0],
+              [0, 0, 0, -1, 0],
+              [0, 0 ,0, 0,  1]])
+
+# NumPy array slicing
+
+A_1_1 = A[0:2,0:3]
+
+A_1_2 = A[0:2,3:]
+# A_1_2 = A[0:2,-2:]
+A_2_1 = A[2:,0:3]
+# A_2_1 = A[-2:,0:3]
+A_2_2 = A[2:,3:]
+# A_2_2 = A[-2:,-2:]
+
+# Assemble a matrix from nested lists of blocks
+
+A_ = np.block([[A_1_1, A_1_2],
+               [A_2_1, A_2_2]])