diff --git a/Book4_Ch01_Python_Codes/Bk4_Ch1_02.py b/Book4_Ch01_Python_Codes/Bk4_Ch1_02.py
deleted file mode 100644
index 8bf7e9e..0000000
--- a/Book4_Ch01_Python_Codes/Bk4_Ch1_02.py
+++ /dev/null
@@ -1,19 +0,0 @@
-
-###############
-# Authored by Weisheng Jiang
-# Book 4  |  From Basic Arithmetic to Machine Learning
-# Published and copyrighted by Tsinghua University Press
-# Beijing, China, 2022
-###############
-
-# Bk4_Ch1_02.py
-
-import numpy as np
-
-# define two column vectors
-a = np.array([[4], [3]])
-b = np.array([[-3], [4]])
-
-# calculate L2 norm
-a_L2_norm = np.linalg.norm(a)
-b_L2_norm = np.linalg.norm(b)