numpy数组运算

数组运算

不需要循环即可对数据进行批量运算，叫做矢量化运算. 不同形状的数组之间的算数运算，叫做广播.

import numpy as np

ndarray1 = np.array([1, 2, 3, 4, 5])
ndarray2 = np.array([3, 4, 5, 6, 7])

# 数组和数组之间的运算
ndarray3 = ndarray1 * ndarray2
ndarray4 = ndarray1 + ndarray2

# 数组和数字值之间的运算
ndarray5 = ndarray1 + 100
ndarray6 = 5 / ndarray1

# 多维数组和多维数组之间的运算
ndarray7 = np.arange(9).reshape((3, 3))
ndarray8 = np.arange(9).reshape((3, 3))
ndarray9 = ndarray7 + ndarray8 

# 一维数组和多维数组之间运算
ndarray10 = np.arange(3)
ndarray11 = np.arange(6).reshape((2, 3))
ndarray12 = ndarray10 + ndarray11

输出结果：

    ndarray3: [ 3  8 15 24 35]
    ndarray4: [ 4  6  8 10 12]
    ndarray5: [101 102 103 104 105]
    ndarray6: [ 5.        2.5         1.66666667  1.25        1.  ]
    ndarray9: [[ 0  2  4]
               [ 6  8 10]
               [12 14 16]]
    ndarray10: [0 1 2]
    ndarray11: [[0 1 2]
                [3 4 5]]
    ndarray12: [[0 2 4]
                [3 5 7]]