Pandas merge or update an empty dataframe with another dataframe?-CodePudding

I have an empty dataframe df1

import numpy as np
import pandas as pd

df1 = pd.DataFrame(columns=['A','B','C','D','E'])

df1
A   B   C   D   E

I want to merge or update this dataframe with another dataframe df2

df2 = pd.DataFrame({ 'B': [1,2,3],
                     'D': [4,5,6],
                     'E': [7,8,9]})
df2
    B   D   E
0   1   4   7
1   2   5   8
2   3   6   9

to get a merged or updated dataframe as

    A   B   C   D   E
0   NaN 1   NaN 4   7
1   NaN 2   NaN 5   8
2   NaN 3   NaN 6   9

Besides, efficiency is required because I have a long df1 and df2.

Any good idea? Thank you.

CodePudding user response：

try this

import pandas as pd
pd.concat((df1, df2))

CodePudding user response：

Use reindex:

df1 = df2.reindex(columns=df1.columns)

Output:

    A  B   C  D  E
0 NaN  1 NaN  4  7
1 NaN  2 NaN  5  8
2 NaN  3 NaN  6  9