数据处理12-2 切片

import numpy as np
# 文件-设置-项目-解释器-找加号，搜索numpy-点击安装
#12-1修改内容
dt = np.dtype([('name','S20'),('age','i1')])
b = np.array([('abc',21),('xyz',18)],dtype = dt) # 把列表嵌套转换成二维数组
print(b)
print('tuple',b.dtype)

x = [1,2,3]
a = np.asarray(x,dtype = int)
print(a)

x = [(1,2,3),(4,5,None)] # 数组的数据类型没有tuple，空值要用None
a = np.asarray(x)
print(a)

x = np.arange(5) #start 默认是0，stop是5，step默认是1
print(x)

num_list= [1,2,3,4,5,6,7,8]
# [2,4]
print(num_list[1:4:2])
# list_name[start:stop:step]

x = np.arange(1,9,1)
print(x[1:4:2])

s = slice(1,4,2)
print(x[s])

print(num_list[s])

a = [[1,2,3],[4,5,6]]
x = np.asarray(a)
print(np.transpose(x))

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