基本参数：axis、skipna
#基本参数：axis、skipnaimport numpy as np1import pandas as pdimport datetimedf = pd.DataFrame({'key1':[4,5,3,np.nan,2], 'key2':[1,2,np.nan,4,5], 'key3':[1,2,3,'j','k']}, index=['a','b','c','d','e'])print...
