Filling an empty (NaN) column with 0 or 1 based on if a value is in a list from another column

Mish :

I have the following data frame:

import pandas as pd
import numpy as np

df = pd.DataFrame({'Q1': ['A,B', 'A,C', 'A,B', 'B,C', 'A,B,C','C,B,A','B,C,A'],
               'Q2': ['B,A', 'C,A', 'B,C,A', 'A,B', 'A,C', 'B,C','C,B'], 
               'Q3': ['C,A', 'C,B', 'A,B', 'C,B', 'A,B,C','A,B,C','C,A']})

df['Q1'] = df['Q1'].apply(lambda x: x.split(','))
df['Q2'] = df['Q2'].apply(lambda x: x.split(','))
df['Q3'] = df['Q3'].apply(lambda x: x.split(','))

colQ1 = df["Q1"].explode().unique()
colQ1df = pd.DataFrame(columns = colQ1)

df = pd.concat([df, colQ1df], sort=False)

print(df)

I want to fill the new column 'A' with a '1' if column 'Q1' contains 'A' and 0 if it does not.

jezrael :

Dont explode values, better is use Series.str.get_dummies with concat if need processing each column same way:

df = pd.DataFrame({'Q1': ['A,B', 'A,C', 'A,B', 'B,C', 'A,B,C','C,B,A','B,C,A'],
               'Q2': ['B,A', 'C,A', 'B,C,A', 'A,B', 'A,C', 'B,C','C,B'], 
               'Q3': ['C,A', 'C,B', 'A,B', 'C,B', 'A,B,C','A,B,C','C,A']})

df = pd.concat([df[x].str.get_dummies(',') for x in df], keys=df.columns, axis=1)
df.columns = df.columns.map('_'.join)
print (df)
   Q1_A  Q1_B  Q1_C  Q2_A  Q2_B  Q2_C  Q3_A  Q3_B  Q3_C
0     1     1     0     1     1     0     1     0     1
1     1     0     1     1     0     1     0     1     1
2     1     1     0     1     1     1     1     1     0
3     0     1     1     1     1     0     0     1     1
4     1     1     1     1     0     1     1     1     1
5     1     1     1     0     1     1     1     1     1
6     1     1     1     0     1     1     1     0     1

If want each column to separate Dataframe:

df1 = df['Q1'].str.get_dummies(',')
print (df1)
 A  B  C
0  1  1  0
1  1  0  1
2  1  1  0
3  0  1  1
4  1  1  1
5  1  1  1
6  1  1  1

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