python-numpy基础学习

import numpy as np
list = [[1,2,3,4],[5,6,7,8],[9,10,11,12],[13,14,15,16]]
df = np.array(list)
print(df)

df[:,1:3]            #取第二列和第三列
df[:,[1,3]]          #取第二列和第四列
df[df<10] = 0                   #小于等于10的数替换为0
df[df>10] = 20             #大于10的数替换为2
t = np.where(df<=10,0,20)        #(条件，满足条件的替换值，不满足条件的替换值)
print(t)
df[np.isnan(df)] = 888     #修改nan为888
print(df.dtype)          #float64
print(np.nan == np.nan)             #false
print(np.count_nonzero(df!=df))    #统计nan个数