有范围和无范围索引时的Numpy行为

import numpy as np

arr = np.array([[1, 2], [3, 4], [5, 6]])
rows = np.array([0, 1, 2])
cols = np.array([1, 0, 1])

selected_elements = arr[rows, cols]
print(selected_elements)  # 输出: [2 3 6]

import numpy as np

arr = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]])

# 获取第二行的所有元素
second_row = arr[1, :]
print(second_row)  # 输出: [4 5 6]

# 获取所有行的第三列元素
third_column = arr[:, 2]
print(third_column)  # 输出: [3 6 9]

import numpy as np

arr = np.array([[1, 2], [3, 4]])
rows = np.array([0, 2])  # 第二个索引2超出了数组的行范围

# 使用np.clip限制索引值
clipped_rows = np.clip(rows, 0, arr.shape[0] - 1)
selected_elements = arr[clipped_rows, :]
print(selected_elements)  # 输出: [[1 2] [3 4]]