Pandas How to mapping two dataframes without remove unique value?

Question

I have two dataframes like this.

df1

  id    value1
0  002     10
1  003     10
2  004     20
3  005     20

df2

   id        value2
0  001        100
1  002        200
2  003        150

I merge dataframe like with this code.

df3 = pd.merge(df1, df2, left_on='id', right_on='id')

The output of this code is.

  id    value1 value2
0  002     10   200
1  003     10   150

I don't want to remove unique data. I want result like this.

  id    value1  value2
  001     100     
  002     10     200
  003     10     150
  004     20
  005     20

How to mapping two data frames without remove unique value?

Answer 1

You can try how=outer

df3 = pd.merge(df1, df2, on='id', how='outer')

print(df3)

   id  value1  value2
0   2    10.0   200.0
1   3    10.0   150.0
2   4    20.0     NaN
3   5    20.0     NaN
4   1     NaN   100.0