如何使用 Pandas 计算两个日期之间的工作日数

Question

I created a pandas df with columns named start_date and current_date. Both columns have a dtype of datetime64[ns]. What's the best way to find the quantity of business days between the current_date and start_date column?

I've tried:

from pandas.tseries.holiday import USFederalHolidayCalendar
from pandas.tseries.offsets import CustomBusinessDay

us_bd = CustomBusinessDay(calendar=USFederalHolidayCalendar())

projects_df['start_date'] = pd.to_datetime(projects_df['start_date'])
projects_df['current_date'] = pd.to_datetime(projects_df['current_date'])

projects_df['days_count'] = len(pd.date_range(start=projects_df['start_date'], end=projects_df['current_date'], freq=us_bd))

I get the following error message:

Cannot convert input....start_date, dtype: datetime64[ns]] of type <class 'pandas.core.series.Series'> to Timestamp

I'm using Python version 3.10.4.

Answer 1

pd.date_range 's parameters need to be datetimes, not series.
For this reason, we can use df.apply to apply the function to each row.
In addition, pandas has bdate_range which is just date_range with freq defaulting to business days, which is exactly what you need.
Using apply and a lambda function, we can create a new Series calculating business days between each start and current date for each row.

projects_df['start_date'] = pd.to_datetime(projects_df['start_date'])
projects_df['current_date'] = pd.to_datetime(projects_df['current_date'])

projects_df['days_count'] = projects_df.apply(lambda row: len(pd.bdate_range(row['start_date'], row['current_date'])), axis=1)

Using a random sample of 10 date pairs, my output is the following:

           start_date        current_date  bdays
0 2022-01-03 17:08:04 2022-05-20 00:53:46    100
1 2022-04-18 09:43:02 2022-06-10 16:56:16     40
2 2022-09-01 12:02:34 2022-09-25 14:59:29     17
3 2022-04-02 14:24:12 2022-04-24 21:05:55     15
4 2022-01-31 02:15:46 2022-07-02 16:16:02    110
5 2022-08-02 22:05:15 2022-08-17 17:25:10     12
6 2022-03-06 05:30:20 2022-07-04 08:43:00     86
7 2022-01-15 17:01:33 2022-08-09 21:48:41    147
8 2022-06-04 14:47:53 2022-12-12 18:05:58    136
9 2022-02-16 11:52:03 2022-10-18 01:30:58    175