You can use the Series.to_list
method.
For example:
import pandas as pd
df = pd.DataFrame({'a': [1, 3, 5, 7, 4, 5, 6, 4, 7, 8, 9],
'b': [3, 5, 6, 2, 4, 6, 7, 8, 7, 8, 9]})
print(df['a'].to_list())
Output:
[1, 3, 5, 7, 4, 5, 6, 4, 7, 8, 9]
To drop duplicates you can do one of the following:
>>> df['a'].drop_duplicates().to_list()
[1, 3, 5, 7, 4, 6, 8, 9]
>>> list(set(df['a'])) # as pointed out by EdChum
[1, 3, 4, 5, 6, 7, 8, 9]