Get data of the day before previous day-CodePudding

I'm trying to make a report on daily balance fluctuations. My idea is make a folder, use glob to open all files, concat and use it to make Scatter chart. Below is my sample code:

import pandas as pd
import numpy as np

df1 = pd.DataFrame({
    'BAS_DT': ['20211010','20211010','20211011','20211011','20211012','20211012'],
    'REF_NO': ["VN121001211","VN121001212","VN121001211","VN121001212","VN121001212","VN121001213"],
    'APPR_LIM':[1,2,1,2,2,3]})
df1.head(6)

#df1

BAS_DT  REF_NO  APPR_LIM
0   20211010    VN121001211 1
1   20211010    VN121001212 2
2   20211011    VN121001211 1
3   20211011    VN121001212 2
4   20211012    VN121001212 2
5   20211012    VN121001213 3

import datetime
Previous_date=datetime.datetime.today() - datetime.timedelta(days=1)
Previous_date = Previous_date.strftime('%Y%m%d')

df2=df1[df1['BAS_DT']==Previous_date]
print(df2)

#df2
     BAS_DT       REF_NO  APPR_LIM
2  20211011  VN121001211         1
3  20211011  VN121001212         2

df3 = df1.tail(2)
print(df3)

#df3
     BAS_DT       REF_NO  APPR_LIM
4  20211012  VN121001212         2
5  20211012  VN121001213         3

After getting data of last day and previous day, I use isin to find out which REF_NO has been deleted:

df2['Match'] = df2['REF_NO'].isin(df3['REF_NO'])
df2 = df2[(df2['Match']==False)]
print(df2)

#df2
     BAS_DT       REF_NO  APPR_LIM  Match
2  20211011  VN121001211         1  False

But problem is if I make report on Monday and actual Previous_date is weekend (No new balance is generated at the weekend), formula df2=df1[df1['BAS_DT']==Previous_date] will return results with nothing.

What should I do in this case?

Thanks and best regards

CodePudding user response：

Instead of minusing datetime.timedelta(days=1), use BDay offset from pandas, which calculates business date offset:

import datetime
from pandas.tseries.offsets import BDay

Previous_date=datetime.datetime.today() - BDay(1)
Previous_date = Previous_date.strftime('%Y%m%d')

Previous_date
'20211008'

Today is 2021-10-11, Monday, the previous business day was 2021-10-08.