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pythondataframeunique

get unique column value by date in python


i've generated this dataframe:

np.random.seed(123)

len_df = 10
groups_list = ['A','B']
dates_list = pd.date_range(start='1/1/2020', periods=10, freq='D').to_list()

df2 = pd.DataFrame()
df2['date'] = np.random.choice(dates_list, size=len_df)
df2['value'] = np.random.randint(232, 1532, size=len_df)
df2['group'] = np.random.choice(groups_list, size=len_df)
df2 = df2.sort_values(by=['date'])
df2.reset_index(drop=True, inplace=True)

        date group  value
0 2020-01-01     A    652
1 2020-01-02     B   1174
2 2020-01-02     B   1509
3 2020-01-02     A    840
4 2020-01-03     A    870
5 2020-01-03     A    279
6 2020-01-04     B    456
7 2020-01-07     B    305
8 2020-01-07     A   1078
9 2020-01-10     A    343

I need to get rid of duplicated groups in the same date. I just want that one group appears only once in a date.

Result

        date group  value
0 2020-01-01     A    652
1 2020-01-02     B   1174
2 2020-01-02     A    840
3 2020-01-03     A    870
4 2020-01-04     B    456
5 2020-01-07     B    305
6 2020-01-07     A   1078
7 2020-01-10     A    343

Solution

  • .drop_duplicates() is in the pandas library and allows you to do exactly that. Read more in the documentation.

    df2.drop_duplicates(subset=["date", "group"], keep="first")
    
    Out[9]: 
            date group  value
    0 2020-01-01     A    652
    1 2020-01-02     B   1174
    3 2020-01-02     A    840
    4 2020-01-03     A    870
    6 2020-01-04     B    456
    7 2020-01-07     B    305
    8 2020-01-07     A   1078
    9 2020-01-10     A    343