How To Replace Dot With Null or Empty Row Using Python Regular Expression

Question

I have a dataframe data that looks this this:

    age
0   .
1   1.2
2   9
3   .

I want to convert all the rows that have . to an empty value (or np.nan).
My desired output would be:

    age
0   
1   1.2
2   9
3   

I tried two different regular expressions which both didn't work:

data['age'] = data['age'].str.replace(r'^(.)$', '')
data['age'] = data['age'].str.replace(r'\D', '')

Both of the results:

    age
0   
1   NaN
2   NaN
3