How to copy the value of one variable to same variable by matching values in another variable in python pandas

Question

I have following dataset

Item Count
A    Sixty
A    
A    
B    
B    Thirty
B    

Code to reproduce:

import pandas as pd
df = pd.DataFrame([
    ['A', 'Sixty'],
    ['A', ],
    ['A', ],
    ['B', ],
    ['B', 'Thirty'],
    ['B', ],
], 
    columns=['Item', 'Count'])

I want to copy the data of 'Count' in empty fields by matching 'Item'.so the output looks like this

Item Count
A    Sixty
A    Sixty
A    Sixty
B    Thirty
B    Thirty
B    Thirty