[FIXED] Merge two dataframes on index, get rid of key_0

Issue

I want to merge two dataframes by the index columns. My code is:

import pandas as pd
import numpy as np
df1 = pd.DataFrame({'a': ['red', 'red', 'red']})
df2 = pd.DataFrame({'b': [1, 2, 2]})

df = df1.merge(df2, how='left', left_on=df1.index, right_on=df2.index)
print(df.head())

   key_0    a  b
0      0  red  1
1      1  red  2
2      2  red  2

The result has an unwanted column key_0. Question: How do I get rid of this column (without any drops after the merge)?

Solution

Instead of treating the index-columns as regular columns, I was able to get rid of the key_0 by using the keywords left_index and right_index:

df = df1.merge(df2, how='left', left_index=True, right_index=True)
print(df.head())

     a  b
0  red  1
1  red  2
2  red  2

Answered By - Carsten