Apply get_dummies with duplicated values in Pandas column

Question

I have a dataframe that look like below:

df=pd.DataFrame([{"id": 'A1', 'words': 'a,b,d,d,e,f,f'},
                   {"id": 'A2', 'words': 'm,b,t,d,e,t,s'},
                   {"id": 'A3', 'words': 's,b,d,e,e,m,m'}])

Note that if a letter appears twice, it should only be counted once. How do I apply get_dummies() to turn it into the below final data frame?

id     a b d e f m s t
A1     1 1 1 1 1 0 0 0
A2     0 1 1 1 0 1 1 1
A3     0 1 1 1 0 1 1 0

I used the below code but it did not work quite as expected, likely due to the duplicated values in the column.

df = df.assign(words = df.words.str.split(',')).explode('words')
df = pd.get_dummies(df, prefix=['words'], columns=['words'])
df

Answer 1

Let us try

out = df.set_index('id')['words'].str.get_dummies(',').reset_index()
Out[171]: 
   id  a  b  d  e  f  m  s  t
0  A1  1  1  1  1  1  0  0  0
1  A2  0  1  1  1  0  1  1  1
2  A3  0  1  1  1  0  1  1  0