将特定列连接到新数据框

Question

I have a data-frame df that looks like:

    A   B   C   D
0  A0  B0  C0  D0
1  A1  B1  C1  D1
2  A2  B2  C2  D2
3  A3  B3  C3  D3

I am trying to concatenate from df the index and columns B and D to a new data-frame called finalDf so my final output for finalDf would look like:

     B    D
0   B0   D0
1   B1   D1
2   B2   D2
3   B3   D3

Please see my code below:

finalDf= pd.DataFrame()

df1 = pd.DataFrame({'A': ['A0', 'A1', 'A2', 'A3'],
    'B': ['B0', 'B1', 'B2', 'B3'],
    'C': ['C0', 'C1', 'C2', 'C3'],
    'D': ['D0', 'D1', 'D2', 'D3']},
     index=[0, 1, 2, 3])

finalDf= pd.concat([finalDf,df1['B','D']])

However running the code above I get a KeyError:

KeyError: ('B', 'D')

What have I done wrong?

Answer 1

It looks like finalDf is empty so it is not necessary to concatenate

You can use

finalDf = pd.DataFrame()
finalDf["B"] = df["B"]
finalDf["D"] = df["D"]