【numpy求和】numpy.sum()求和

2023-08-21 10:24| 来源: 网络整理| 查看: 265

numpy.sum(a, axis=None, dtype=None, out=None, keepdims=, initial=)[source])用于计算array元素的和.

python中常用的numpy进行数学计算，其中array的求和运算分为两种，一种是调用numpy.array自身的sum()方法,另一种是利用numpy的内建函数numpy.sum()使用。(tips:python从0开始计数axis=0对应第一个维度)

#example import numpy as np x = np.random.rand(2,3,4) #生成三维随array print("This is a 2*3rows 4cols array\n",x) ''' >>> This is a 2*3rows 4cols array [[[ 0.88264952 0.12446208 0.82166137 0.31747846] [ 0.51436626 0.03051283 0.46987831 0.64086531] [ 0.14819094 0.6395191 0.21753309 0.61340538]] [[ 0.0878878 0.5317064 0.65523138 0.704961 ] [ 0.51081521 0.88710145 0.92958269 0.89587262] [ 0.60233393 0.26146419 0.26584161 0.0823285 ]]] ''' print('instance method:',x.sum()) print('numpy function:',np.sum(x)) ''' >>> 'instance method:', 11.835649415181807 >>> 'numpy function:', 11.835649415181807 ''' #对特定的轴求和 print('First axis sum',x.sum(axis=0)) ''' >>> 'First axis sum', #第一维是轴0，对前后两页array加和得到3*4的array输出 array([[ 0.97053732, 0.65616848, 1.47689275, 1.02243946], [ 1.02518147, 0.91761428, 1.399461 , 1.53673793], [ 0.75052486, 0.90098329, 0.4833747 , 0.69573388]]) ''' print('Second axis sum',x.sum(axis=1)) ''' >>> 'Second axis sum', #第二维是轴1，将每列的三行进行sum（对行求sum），得到2*4的输出 array([[ 1.54520672, 0.79449401, 1.50907277, 1.57174914], [ 1.20103694, 1.68027204, 1.85065568, 1.68316212]]) ''' print('Third axis sum',x.sum(axis=2)) ''' >>> 'Third axis sum', #第三维是轴2，有4个数，将每行四个数加和（对列求sum），得到2*3输出 array([[ 2.14625142, 1.65562271, 1.6186485 ], [ 1.97978658, 3.22337197, 1.21196823]]) ''' #对多个轴求和 print('axis1,2 sum:',x.sum(axis=(1,2))) ''' >>> 'axis1,2 sum: #对第二维(axis=1)和第三维(axis=2)求和，归在第一维(axis=0)上 array([ 5.42052263, 6.41512678]) '''

在这里插入图片描述 pic from pexels

ref: https://docs.scipy.org/doc/numpy/reference/generated/numpy.ndarray.sum.html https://docs.scipy.org/doc/numpy/reference/generated/numpy.sum.html https://blog.csdn.net/Leekingsen/article/details/76242244 https://blog.csdn.net/addmana/article/details/78472608

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