Condition Based Custom Flag

Question

I've a dataset

id	ref	name	conditionCol
1	123	a	no_error
1	456	b	error
1	789	c	no_error
2	231	d	no_error
2	312	e	no_error
2	546	f	no_error
3	645	g	error
3	879	h	error
4	789	i	no_error
4	978	j	no_error

I'm trying to create a custom error_flag, condition being:

• for each unique id column elements
• if any row in the conditionCol has the keyword error, then
• for each row should be flagged as yes in the error_flag
• if for any element in id column
• not even a single row has the keyword error in conditionCol column, then
• for each row should be flagged as no in the error_flag

E.g. For id:1, all the values of error_flag is yes, as for id value 1, row #2 of conditionCol has error

id	ref	name	conditionCol	error_flag
1	123	a	no_error	yes
1	456	b	error	yes
1	789	c	no_error	yes

But, for id:2, all the values of error_flag is no, as for id value 2, no row of conditionCol has error

id	ref	name	conditionCol	error_flag
2	231	d	no_error	no
2	312	e	no_error	no
2	546	f	no_error	no

Similarly for id value 3 & 4:

id	ref	name	conditionCol	error_flag
3	645	g	no_error	no
3	879	h	no_error	no
4	789	i	error	yes
4	978	j	error	yes

And final output being:

id	ref	name	conditionCol	error_flag
1	123	a	no_error	yes
1	456	b	error	yes
1	789	c	no_error	yes
2	231	d	no_error	no
2	312	e	no_error	no
2	546	f	no_error	no
3	645	g	no_error	no
3	879	h	no_error	no
4	789	i	error	yes
4	978	j	error	yes

Update:

If you wish to play around with the dataset:

import pandas as pd
import numpy as np

id_col = [1,1,1,2,2,2,3,3,4,4]
ref_col = [123,456, 789, 231, 312, 546, 645, 879, 789, 978]
name_col = ['a','b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j']
conditionCol = ['no_error', 'error', 'no_error', 'no_error', 'no_error', 'no_error', 'no_error', 'no_error', 'error', 'error']
df = pd.DataFrame(zip(id_col, ref_col, name_col, conditionCol), columns=['id','ref','name','conditionCol'])
df

update2: Is there a way to work with thresholds, i.e.:

• current question: atleast one occurrence of keyword error in conditionCol column for each individual unique ids, then the value in error_flag would be yes for all the rows in that id value
• atleast 4 or atleast 5 occurrence of keyword error in conditionCol column for unique ids, then only the value in error_flag would be yes for all the rows in that id value

Answer 1

Use numpy.where with test if at least one value error per groups by id:

m = df['id'].isin(df.loc[df['conditionCol'].eq('error'), 'id'])
#alternative
#m = df['conditionCol'].eq('error').groupby(df['id']).transform('any')
df['error_flag'] = np.where(m, 'yes', 'no')

print (df)
   id  ref name conditionCol error_flag
0   1  123    a     no_error        yes
1   1  456    b        error        yes
2   1  789    c     no_error        yes
3   2  231    d     no_error         no
4   2  312    e     no_error         no
5   2  546    f     no_error         no
6   3  645    g     no_error         no
7   3  879    h     no_error         no
8   4  789    i        error        yes
9   4  978    j        error        yes