merge pandas

df_3 = pd.concat([df_1, df_2])

Here is what the above code is Doing:
1. Creating a new DataFrame called df_3 that is a concatenation of df_1 and df_2.
2. Creating a new DataFrame called df_4 that is a concatenation of df_1 and df_2, but with the rows in reverse order.
3. Creating a new DataFrame called df_5 that is a concatenation of df_1 and df_2, but with the columns in reverse order.