How to change the date time format for only SOME ROWS in Pandas?-CodePudding

I have a dataframe in which there are some columns. One of them is Date but some dates are in the format of dd-MMM-YY (eg: 03-May-2022) and some are in the format dd-mm-yy(eg: 03-05-2022). How do I change all the dates in the column to one format(eg: dd-mm-yy)?

Initial Dataframe:

Serial	Date
0	23-05-2022
1	14-Mar-2022
2	29-02-2020

Required Output:

Serial	Date
0	23-05-2022
1	14-03-2022
2	29-02-2020

CodePudding user response：

I can think of one solution where you handle the two different cases based on length of the date string:

def format_date(date):
    reformatter = {
        "Jan": "01",
        "Feb": "02",
        "Mar": "03",
        ...
        "Dec": "12"

    }
    if len(date) == 10:
        return date
    else:
        return date[:4]   reformatter[date[3:6]]   date[6:]

df["Date"].apply(lambda x: format_date(x))

CodePudding user response：

You can try to use automatic date parsing:

df['Date'] = (pd.to_datetime(df['Date'], infer_datetime_format=True)
                .dt.strftime('%d-%m-%Y')
              )

Or, using str.replace:

from calendar import month_abbr

d = dict(zip(month_abbr, [f'{i:02d}' for i in range(13)]))

df['Date'] = df['Date'].str.replace(r'[A-Z][a-z] ', lambda x: d.get(x.group(), x), regex=True)

Output:

   Serial        Date
0       0  23-05-2022
1       1  14-03-2022
2       2  29-02-2020