Creating a new column in dataframe after groupby

Question

I have the following type of dataframe:

import pandas as pd
data = {
    'Uni' : ['FUNDP','FUNDP','FUNDP','Ulg','Ulg','ULB'],
    'data': [1.1,1.1,1.1,2.0,2.0,1.]
    
}
df=pd.DataFrame(data)

I would like to count the number of times I have the same values in column Uni and pass the result into a new column called Count. Here is an example of the outcome I'm looking for:

Uni    data Count
FUNDP   1.1 3
FUNDP   1.1 3
FUNDP   1.1 3
Ulg     2.0 2
Ulg     2.0 2
ULB     3.0 1