Assign pandas dataframe column value based on first ocurrence

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

>Solution :

try via groupby()+transform():

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

OR

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

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