Python：在 dataframe 中获取唯一日期

Question

I have a data frame that looks like this:

                       price
Date
2022-01-01 19:20:00    100   
2022-01-01 19:27:00    100
2022-01-02 19:31:00    102

I want the dataframe to only have unique dates:

                       price
Date
2022-01-01 19:20:00    100   
2022-01-02 19:31:00    102

How can I achieve that?

Answer 1

You can sort the dataframe with:

df = df.sort_values('Date')

And than leave only the rows with a new date with:

df = df[df['Date'].dt.date != df['Date'].shift().dt.date]

Answer 2

You can extract the date from the datetime column using df.Date.dt.date , put that into a new column using assign , and after that use drop_duplicates based on only that column. Last, you might want to drop the newly create column that has only the date information. In code that reads

df = (
    df.assign(new_date=lambda df:df.Date.dt.date)
   .drop_duplicates(subset=["new_date"])
   .drop(columns=["new_date"])
)

Answer 3

You can simply use duplicated :

# pre-requisite
df['Date'] = pd.to_datetime(df['Date'])

df[~df['Date'].dt.date.duplicated()]

Or if working with the index:

df[~df.index.to_series().dt.date.duplicated().values]

Output:

                 Date  price
0 2022-01-01 19:20:00    100
2 2022-01-02 19:31:00    102