select elements in df pandas according to another column value in df

Question

I have my df as following:

In [2]: df Out[2]:

    A  B  C
0  b1  1  0
1  b2  1  0
2  b1  3  1
3  b1  2  1
4  b2  2  1
5  b2  4  1

I want to use a pandas command to just select elements according the column B:

In [2]: df_new Out[2]:

   A  B  C
0  b1  1  0
1  b2  1  0
3  b1  2  1
4  b2  2  1

Cheers, Behzad.

Hi jezrael, but what I have in 'B' is not always 1 and 2. I want to say select all elements in 'A' if they have same 'B' when their 'C' is the same. — bzdhss, Apr 25 '18 at 13:15

score 1 · Accepted Answer · answered Apr 25 '18 at 13:18

1

Use DataFrame.duplicated for boolean mask by 2 columns and keep=False for return all dupes and filter by boolean indexing:

df = df[df.duplicated(['B', 'C'], keep=False)]
print (df)
    A  B  C
0  b1  1  0
1  b2  1  0
3  b1  2  1
4  b2  2  1

answered Apr 25 '18 at 13:18

jezrael

1 Answers1