【笔记】mask（遮挡）的实现方法 && set( ) 会将数据元素打乱 && 列表元素为＜class ‘int‘＞,直接赋值以小数会向下取整

def safe_log(x):
    mask = x != 0
    print(mask)
    print(x[mask])
    print(np.log(x[mask]))
    x[mask] = np.log(x[mask])
    print(x)
    return x

import numpy as np
x=np.array([1.,2,3])

print(safe_log(x))


y=np.array([1,2,3,4,5,6,7,8])
y[0]=5.7
print(y)

mask1=[True,False,True,False,True,False,True,False]
print(y[mask1])
print(y[[True,False,True,False,True,False,True,False]])
# print(y[True False True False True False True False]) # SyntaxError: invalid syntax
print(y[True,False,True,False,True,False,True,False])  # print(y[])  SyntaxError: invalid syntax

print("False") if y[0]==8 else print("True")
mask2 = y!=8

print(mask2)
print(y[mask2])

xx=np.array([[1,2,3],[4,5,6]])
print(xx==1)


z=[1000,10000,111,11111,1112222,222334,5,556,666]

import itertools
print(set(itertools.chain(y,z)))
print(list(itertools.chain(y,z)))


print(set(z))

[ True  True  True]
[1. 2. 3.]
[0.         0.69314718 1.09861229]
[0.         0.69314718 1.09861229]
[0.         0.69314718 1.09861229]
[5 2 3 4 5 6 7 8]
[5 3 5 7]
[5 3 5 7]
[]
True
[ True  True  True  True  True  True  True False]
[5 2 3 4 5 6 7]
[[ True False False]
 [False False False]]
{2, 3, 4, 5, 6, 7, 8, 1000, 11111, 556, 111, 10000, 666, 222334, 1112222}
[5, 2, 3, 4, 5, 6, 7, 8, 1000, 10000, 111, 11111, 1112222, 222334, 5, 556, 666]
{5, 11111, 1000, 556, 111, 10000, 666, 222334, 1112222}

Process finished with exit code 0