Subsetting dataframe by same values in two columns

Question

I have a dataframe that looks like below:

code_1	code_2
a1	a1
a2	a1
b1	b2
b3	b3

What I want to do here is that I want to subset the dataframe by selecting the rows that have same values in 'code_1' and 'code_2'

The final output would look like below:

code_1	code_2
a1	a1
b3	b3

Thank you

Answer 1

Let's try query

Code

df.query('code_1 == code_2')

Output

    code_1  code_2
0   a1      a1
3   b3      b3

If we want the index to be sequential

df.query('code_1 == code_2').reset_index(drop=True)

Output

    code_1  code_2
0   a1      a1
1   b3      b3

More details about query can be found here