Calculating number of business days between two dates in pandas

Question

I have a following problem. I would like to calculate number of business days between two dates. Example:

import numpy as np

pokus = {"start_date" : "2022-01-01 10:00:00" , "end_date" : "2022-01-01 17:00:00" }
df = pd.DataFrame(pokus, index=[0])
cas_df["bus_days"] = np.busday_count(pd.to_datetime(df["start_date"]) , pd.to_datetime(df["end_date"]))

Which returns a confusing error:

Traceback (most recent call last):
  File "/home/vojta/.local/lib/python3.8/site-packages/IPython/core/interactiveshell.py", line 3251, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-17-8910d714721b>", line 3, in <module>
    cas_df["bus_days"] = np.busday_count(pd.to_datetime(df["start_date"]) , pd.to_datetime(df["end_date"]))
  File "<__array_function__ internals>", line 180, in busday_count
TypeError: Iterator operand 0 dtype could not be cast from dtype('<M8[ns]') to dtype('<M8[D]') according to the rule 'safe'

How can I fix it please?

Asked By: vojtam

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Source

Answer 1

Try this:

cas_df["bus_days"] = np.busday_count(pd.to_datetime(df["start_date"]).values.astype('datetime64[D]') , pd.to_datetime(df["end_date"]).values.astype('datetime64[D]'))

Answered By: YfNk

Answer 2

np.busday_count
accepts only datetime64[D], but pandas Dataframes and Series can only hold datetime64[ns], as explained in this answer.

So what we can do is convert the start and end date columns to a numpy array (as type datetime64[D]), and then pass these values to np.busday_count:

days = df[['start_date', 'end_date']].to_numpy(dtype='datetime64[D]')
cas_df["bus_days"] = np.busday_count(days[:, 0], days[:, 1])

( you could also use .to_numpy().astype('datetime64[D]') )

Answered By: Vladimir Fokow

Calculating number of business days between two dates in pandas

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