Assign pandas dataframe column value based on first ocurrence-CodePudding

I have a dataframe df1 :-

I want to achieve this transformation in df1:-

Wherever chcolate has ocurrence count>1 ,Based on first ocurrence assign the brand the same value

CodePudding user response：

something like this should work where we groupby chcolate and replace the brand with the first element from that group

df['brand'] = df.groupby('chcolate')['brand'].transform(lambda r:r.iloc[0])

CodePudding user response：

try via groupby() transform():

df['brand'] = df.groupby('chcolate')['brand'].transform('first')

If you want orderwise then use sort_values() first then groupby() transform():

df['brand'] = df.sort_values('brand').groupby('chcolate')['brand'].transform('first')