在不使用for循环的numpy数组中查找元素的索引

import numpy as np

# 创建一个示例数组
arr = np.array([1, 2, 3, 4, 5, 6, 7, 8, 9])

# 查找元素5的索引
index = np.where(arr == 5)

print(index)

(array([4]),)

import numpy as np

# 创建一个示例数组
arr = np.array([1, 2, 3, 4, 5, 6, 7, 8, 9, 5])

# 查找所有元素5的索引
indices = np.argwhere(arr == 5)

print(indices)

[[4]
 [9]]

import numpy as np

# 创建一个示例数组
arr = np.array([1, 2, 3, 4, 5, 6, 7, 8, 9])

# 查找元素5的索引
mask = np.isin(arr, 5)
index = np.where(mask)

print(index)

(array([4]),)

# 对于单个元素的索引
index = np.where(arr == 5)[0][0]

# 对于多个元素的索引
indices = np.argwhere(arr == 5).flatten()

# 查找所有元素5的索引
indices = np.argwhere(arr == 5)

print(indices)

[[4]
 [9]]