pandas errors with attempt to cont unique

Question

I have been trying for a while but keep getting following error. I have the following df

object article
aa       123     
aa       124 
ab       123
ab       123
ac       123
ac       125
ad       123
ad       125

what I want is:

object Count_unique_arcicle
aa       2
ab       1
ac       2
ad       2

what i get is:

object Count_unique_arcicle
aa      nan
ab      nan
ac      nan
ad      nan

Ive tried the following with no luck.

df= sql_query[['object ', 'article']]

df['Count_unique_arcicle'] = df['object'].groupby(df['object ']).transform('count') 

df['Count_unique_arcicle'] = df['object'].groupby(df['object']).nunique()```