numpy：数组比较

m=np.array([
    [1,2,3],
    [10,20,30],
    [35,45,55]
])

n=(m==20)
print(n)

[[False False False]
 [False  True False]
 [False False False]]

col2=(m[:,1]==20)
print(col2)

[False  True False]

print(m[col2,:])

[[10 20 30]]

vector=np.array([5,10,15,20])
ten_or_five=(vector==10)|(vector==5)
print(ten_or_five)

[ True  True False False]

vector[ten_or_five]=50
print(vector)

[50 50 15 20]

import numpy as np
m=np.array([
    [1,2,3],
    [10,20,30],
    [35,45,55]
])

column2=m[:,1]==20
print(column2)

[False  True False]

m[column2,1]=100
print(m)

[[  1   2   3]
 [ 10 100  30]
 [ 35  45  55]]

import numpy as np
m=np.array([
    ['','2','3'],
    ['10','20','30'],
    ['35','45','']
])

col=(m=='')
print(col)

[[ True False False]
 [False False False]
 [False False  True]]

print(col[:,0])

[ True False False]

m[col[:,0],0]='0'
print(m)

[['0' '2' '3']
 ['10' '20' '30']
 ['35' '45' '']]

print(col[:,2])

[False False  True]

m[col[:,2],2]='0'
print(m)

[['0' '2' '3']
 ['10' '20' '30']
 ['35' '45' '0']]