Python Numpy学习之索引及切片的使用方法

"""
Author:XiaoMa
date:2021/12/30
"""
import numpy as np
 
a = np.arange(10)#创建一个从0-9的一维数组
print(a)
i = slice(2, 7, 2)#从2开始到7结束，每隔1个元素进行索引，即start为1，stop为7，step为2
print(a[i])

"""
Author:XiaoMa
date:2021/12/30
"""
import numpy as np
 
a = np.arange(10)#创建一个从0-9的一维数组
print(a[2:7:2])#将起始、结束、步长使用冒号进行分割，表示索引切片

"""
Author:XiaoMa
date:2021/12/30
"""
import numpy as np
 
a = np.arange(10)#创建一个从0-9的一维数组
print(a[2:5])#从2-5进行切片

"""
Author:XiaoMa
date:2021/12/30
"""
import numpy as np
 
a = np.arange(10)#创建一个从0-9的一维数组
print(a[3:])#从3开始进行打印，直到打印完整个数组

"""
Author:XiaoMa
date:2021/12/30
"""
import numpy as np
 
b = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]])
print('从数组索引a[2:]处开始切片：')
print(b[2:])
print('数组第二列进行切片：')
print(b[..., 2])
print('数组第二行进行切片：')
print(b[2, ...])
print('从第二列开始切片：')
print(b[..., 1:])

"""
Author:XiaoMa
date:2021/12/30
"""
import numpy as np
 
b = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]])
c = b[[1, 0], [1, 0]]
print('对数组(1，1)和(0，0)处的元素进行索引切片：')
print(c)

"""
Author:XiaoMa
date:2021/12/30
"""
import numpy as np
 
a = np.array([[1, 2, 3, 5], [6, 9, 2, 0], [9, 3, 2, 7]])
print('数组中不小于5的数如下：')
print(a[a >= 5])

"""
Author:XiaoMa
date:2021/12/30
"""
import numpy as np
 
x = np.arange(32).reshape((8, 4))
print('生成的数组为：')
print(x)
print('传入顺序索引数组：')
print(x[[4, 2, 1, 7]])
print('传入倒序索引数组：')
print(x[[-4, -2, -1, -1]])
print('传入多个索引数组：')
print(x[np.ix_([1, 5, 7, 2], [0, 3, 1, 2])])#输出的是两个向量不同维度组合的值