import pandas as pd
import numpy as np
a = pd.DataFrame(np.random.randint(1,6,(5,3)),index=['a','b','c','d','e'],columns=['one','two','three'])a.loc['a','one'] = np.nan
b = a.iloc[1:3,0:2].values
a['four'] = 'bar'
a2 = a.reindex(['a','b','c','d','e','f'])
a3 = a2.dropna()print("学号:3008")
结果如下