Pandas multiple comparison on a single row

Question

My source data looks like this:

data = { 'id': [1,2,3,4,5],
         '1_src1': ['a', 'b','c', 'd', 'e'] ,
       '1_src2': ['a', 'b','c', 'd', 'e'] ,
       '2_src1': ['a', 'b','f', 'd', 'e'] ,
       '2_src2': ['a', 'b','c', 'd', 'e'] ,
       '3_src1': ['a', 'b','c', 'd', 'e'] ,
       '3_src2': ['a', 'b','1', 'd', 'm'] }
pd.DataFrame(data)

I need to compare Second column with Third, Fourth Column with Fifth Column, Sixth with Seventh.
Column names can change. So I have to consider the column positions and my first column with always has column name as id.

so if atleast one of comparisons (‘1_src1’ vs ‘1_src2’) ( ‘2_src1’ vs ‘2_src2’) fails if need to update 1 else 0.
But if the comparison of (3_src1 vs 3_src2) fails if need to update 2 else 0.

My result should look like :

The code I tried :

I tried creating subset of columns like this. But I am unable to proceed how can I achieve this result.

cols_comp = []
for i in range(0,len(x),2):
    cols_comp.append(x[i:i+2])

Any help appreciated. Thanks.

@Edit:
Adding one more condition:
Right now, if my last comparison fails I am updating ‘res’ as 2 but how can I update ‘res’ as 2 if my last n comparison fails?

Asked By: usr_lal123

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Source

Answer 1

First I make three seperate condition columns based on your 3 comparisons. Then apply these to your rules.

df = pd.DataFrame(data)

cond1 = df.iloc[:, 1] != df.iloc[:, 2]
cond2 = df.iloc[:, 3] != df.iloc[:, 4]
cond3 = df.iloc[:, 5] != df.iloc[:, 6]

df['res'] = 0
df.loc[cond1 | cond2, 'res'] = 1
df.loc[cond3, 'res'] = 2

Answered By: T C Molenaar

Answer 2

You can use:

import numpy as np

# compare columns by pair after 1st one
comp = df.iloc[:, 1::2].ne(df.iloc[:, 2::2].to_numpy())

# select rules
                     # True in last     # True in first 2 comp
df['res'] = np.select([comp.iloc[:, 2], comp.iloc[:, :2].any(1)],
                      [2, 1], # matching values
                      0) # default

output:

   id 1_src1 1_src2 2_src1 2_src2 3_src1 3_src2  res
0   1      a      a      a      a      a      a    0
1   2      b      b      b      b      b      b    0
2   3      c      c      f      c      c      1    2
3   4      d      d      b      d      d      d    1
4   5      e      e      e      e      e      m    2

Answered By: mozway

Pandas multiple comparison on a single row

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