How to use nonzero() in python numpy

This time I will bring you python How to use nonzero() in numpy, what are the precautions for using nonzero() in python numpy, the following is a practical case, one Get up and take a look.

nonzeroFunctionReturns the directory of nonzero elements.

The return value is a tuple, the two values ​​are two dimensions respectively, and contain the directory values ​​of non-zero elements in the corresponding dimensions.

  import numpy as np
  A = np.mat([[0,1,2,3,4,3,2,1,0],[0,1,2,3,4,5,6,7,0]])
  x = A.nonzero() #取出矩阵中的非零元素的坐标
  print x  #输出是一个元组，两个维度。一一对应，
  #返回非零元素在矩阵中的位置,前一个列表存放非零行坐标，后一个列表存放非零元素列坐标
  #(array([0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1]), array([1, 2, 3, 4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7]))
  #放下来一一对应，即
  #(array([0,  0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1,  1,  1]),
   #array([1,  2, 3, 4, 5, 6, 7, 1, 2, 3, 4, 5,  6,  7]))
    # (0,1) (0,2).............................. (1,6) (1,7) 坐标上的元素都是非0的 
  print A[x],'\n'  #取出矩阵中的非零元素
  #[[1 2 3 4 3 2 1 1 2 3 4 5 6 7]] 
  B = np.mat([[1,1,0,1,0,1,0,0,1],[0,1,1,0,0,0,1,1,1]])
  print np.nonzero(B) # 与B.nonzero()等价

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