numpy基础

1、numpy基本使用

`import numpy as np`
`import pandas as pd`
`print(pd.__version__)`
`print(np.__version__)`

``import numpy as np`
`import pandas as pd`
`arr=np.array([1,2,3])  #一维数组`
`print(arr)`
`print("arr.shape：",arr.shape)        #形状`
`print("arr.ndim：",arr.ndim)        #维度`
`print("arr.size：",arr.size)         #大小`
`print("arr.dtype：",arr.dtype)        #元素类型`
print("arr.type：",type(arr))`   

2、创建一个有规则的数组

`#三个参数：起点。终点。步长`
`import numpy as np`
`a=np.arange(10)`
`a`