results = set()
df['text'].str.lower().str.split().apply(results.update)
# get the unique values (rows)
df.drop_duplicates()
In [33]: df[df.columns[df.apply(lambda s: len(s.unique()) > 1)]]
Out[33]:
A B
0 0 a
1 1 b
2 2 c
3 3 d
4 4 e
results = set()
df['text'].str.lower().str.split().apply(results.update)
$ set(['someone', 'ft.jgt', 'my', 'is', 'to', 'going', 'place', 'nickname'])