2.41

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()