Python学习笔记5：Numpy.array()

numpy.array()可以快速建立任意维度的矩阵ndarray

 import numpy as np
 a = np.arange(90).reshape(9,10)  
 a

array([[ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9],
       [10, 11, 12, 13, 14, 15, 16, 17, 18, 19],
       [20, 21, 22, 23, 24, 25, 26, 27, 28, 29],
       [30, 31, 32, 33, 34, 35, 36, 37, 38, 39],
       [40, 41, 42, 43, 44, 45, 46, 47, 48, 49],
       [50, 51, 52, 53, 54, 55, 56, 57, 58, 59],
       [60, 61, 62, 63, 64, 65, 66, 67, 68, 69],
       [70, 71, 72, 73, 74, 75, 76, 77, 78, 79],
       [80, 81, 82, 83, 84, 85, 86, 87, 88, 89]]

# 如果取a的某一行，将降维返回一个一维数组
print(a[0])
a[0].shape

[0 1 2 3 4 5 6 7 8 9]

(10,)

# 如果想要保持维度不变，返回一个1×10的二维数组
b = a[0:1]
print(b)
b.shape
type(b)

[[0 1 2 3 4 5 6 7 8 9]]

numpy.ndarray