Count percentage of upper case words

I would like to determine the percentage of upper case words in texts

Sent

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The below code should be able to determine the percentage of upper case (I think), but not for words but character (and in a string):

alph = list(filter(str.isalpha, s))  
sum(map(str.isupper, alph)) / len(alph)

For looking at the upper case words in each row, I tried as follows:

df['UP'] = df['Sent'].str.findall(r'b([A-Z]{2,})')

and this should work. However I do not know how to calculate the percentage. I hope you can give me some tips on how to calculate it. I think I would count the number of words in each row but I do not know how to do it.

df['UP'] = df['Sent'].str.findall(r'[A-Z]').str.len()

df['Sent'].str.count(r'[A-Z]')