I have a pandas dataframe that looks like this:
import pandas as pd
import numpy as np
arrays = [np.array(['bar', 'bar', 'baz', 'baz', 'foo', 'foo', 'qux', 'qux']),
np.array(['one', 'two', 'one', 'two', 'one', 'two', 'one', 'two'])]
df = pd.DataFrame(np.random.randn(8,4),index=arrays,columns=['A','B','C','D'])
我想添加一个名为
E
的列,并将df.loc[(slice(None),'one'),'E'] = 1
和df.loc[(slice(None),'two'),'E'] = 2
,但我不想遍历['one', 'two']
。我尝试了以下方法:df.loc[(slice(None),slice('one','two')),'E'] = pd.Series([1,2],index=['one','two'])
但是它只是添加了一个带有 NaN
的列 E
。正确的做法是什么?