Round off date in data frame in Python

Question

This is my dataframe

     ID       Date    Value Final Value
0   9560    12/15/2021  30  5.0
1   9560    07/3/2021   25  5.0
2   9560    03/03/2021  20  20.0
3   9712    08/20/2021  15  5.0
4   9712    12/31/2021  10  10.0
5   9920    04/11/2021  5   5.0

Here I need to create a another column 'Round Date'. Get the date from 'Date' column if date is greater than 15 Date should be round off to the beginning date of that month or else begininng date of next month. The expected output is given below.

     ID       Date    Value Final Value  Round Date
0   9560    12/15/2021  30  5.0          12/01/2021
1   9560    07/3/2021   25  5.0          07/01/2021
2   9560    03/03/2021  20  20.0         03/01/2021
3   9712    08/20/2021  15  5.0          09/01/2021
4   9712    12/31/2021  10  10.0         01/01/2022
5   9920    04/11/2021   5   5.0         04/01/2021 

Answer 1

here is the code to round date:

from dateutil import relativedelta
import pandas as pd

# function to round date
def round_date(date):
    # check if day is greater than 15
    if date.day > 15:
        # change month to next month
        date += relativedelta.relativedelta(months=1)    
    # change day to start of month
    date = date.replace(day=1)
    # return date
    return date

# read data frame
df = pd.read_csv('your-path')
# change date column to datetime
df['Date'] = pd.to_datetime(df['Date'] )
# apply round date function to column
df['Round Date'] = df['Date'].apply(round_date)

Answer 2

Using numpy's where :

import pandas as pd
import numpy as np

df["Date"] = pd.to_datetime(df.date)
df["date.rounded"] = np.where(
    df.Date.dt.day > 15,
    df.Date + pd.offsets.MonthBegin(0),
    df.Date + pd.offsets.MonthEnd(0) - pd.offsets.MonthBegin(1)
)

This yields:

    Date      date.rounded
0   2021-12-15  2021-12-01
1   2021-07-03  2021-07-01
2   2021-03-03  2021-03-01
3   2021-08-20  2021-09-01
4   2021-12-31  2022-01-01
5   2021-04-11  2021-04-01

Answer 3

Here is a solution using apply() and lambda

1. Convert values in Date column to datetime using pd.to_datetime()
2. use apply() and lambda function to set day to 1 and increase month value if condition day is greater than 15

Code:

import pandas as pd
from datetime import timedelta
from dateutil.relativedelta import relativedelta

df = pd.DataFrame({'Date': ['2/1/2021', '01/31/2021', '12/31/2021', '2021-12-01']})
df.Date = pd.to_datetime(df.Date)
df['Round Date'] = df.Date.apply(lambda x: x.replace(day=1)+ relativedelta(months=1)  
                                 if x.day > 15 
                                 else x.replace(day=1))

Input:

    Date
0   2/1/2021
1   01/31/2021
2   12/31/2021
3   2021-12-01

Output:

    Date        Round Date
0   2021-02-01  2021-02-01
1   2021-01-31  2021-02-01
2   2021-12-31  2022-01-01
3   2021-12-01  2021-12-01