Answers for "find unique value with related other column pandas"

dataframe unique values in each column

for col in df:
    print(df[col].unique())

find unique elements in pandas and their connection with other column

df = pd.DataFrame({'author':['a', 'a', 'b'], 'subreddit':['sr1', 'sr2', 'sr2']})

>>> df
  author subreddit
0      a       sr1
1      a       sr2
2      b       sr2
...