Use the unique() function to return a new Series object with only the the unique or distinct values in the Series.
>>> df = DataFrame.from_query('select admitted from admissions_train')
>>> s = df.squeeze(axis = 1)
>>> s
0 1
1 1
2 0
3 0
4 1
5 0
6 1
7 0
8 0
9 1
Name: admitted, dtype: object
>>> s.unique() 0 0 1 1 Name: admitted, dtype: object