Python – Get Most recent previous business day

Given a date, the task is to write a Python program to get the most recent previous business day from the given date.

Example:

Input : test_date = datetime(2020, 1, 31)

Output : 2020-01-30 00:00:00

Explanation : 31 Jan 2020, being a Friday, last business day is thursday, i.e 30 January.

Input : test_date = datetime(2020, 2, 3)

Output : 2020-01-31 00:00:00

Explanation : 3 Feb 2020, being a Monday, last business day is friday, i.e 31 January.

Method 1: Using timedelta() + weekday()

In this, we perform the task of subtracting 3 in the case of Monday, 2 in the case of Sunday, and 1 on all other days. The timedelta() performs the task of subtraction, and conditional statements check for a weekday.

Python3

# Python3 code to demonstrate working of
# Last business day
# using timedelta() + conditional statements + weekday()
from datetime import datetime, timedelta

# initializing dates
test_date = datetime(2020, 1, 31)

# printing original date
print("The original date is : " + str(test_date))

# getting difference
diff = 1
if test_date.weekday() == 0:
    diff = 3
elif test_date.weekday() == 6:
    diff = 2
else :
    diff = 1

# subtracting diff
res = test_date - timedelta(days=diff)

# printing result
print("Last business day : " + str(res))

Output:

The original date is : 2020-01-31 00:00:00
Last business day : 2020-01-30 00:00:00

Method 2: Using max() + % operator + timedelta()

Perform tasks in similar way, only difference being method to compute difference changes to get max() and % operator. 

Python3

# Python3 code to demonstrate working of
# Last business day
# using max() + % operator + timedelta()
from datetime import datetime, timedelta

# initializing dates
test_date = datetime(2020, 1, 31)

# printing original date
print("The original date is : " + str(test_date))

# getting difference
# using max() to get differences
diff = max(1, (test_date.weekday() + 6) % 7 - 3)

# subtracting diff
res = test_date - timedelta(days=diff)

# printing result
print("Last business day : " + str(res))

Output:

The original date is : 2020-01-31 00:00:00
Last business day : 2020-01-30 00:00:00

Method 3 : Using pd.tseries.offsets.BusinessDay(n) 

In this, we create a Business day offset of 1 day, and subtract from the date initialized. This returns the previous business day as desired.

Python3

# Python3 code to demonstrate working of
# Last business day
# using pd.tseries.offsets.BusinessDay(n)
import pandas as pd
from datetime import datetime

# initializing dates
test_date = datetime(2020, 2, 3)

# printing original date
print("The original date is : " + str(test_date))

# Creating Timestamp
ts = pd.Timestamp(str(test_date))

# Create an offset of 1 Business days
offset = pd.tseries.offsets.BusinessDay(n=1)

# getting result by subtracting offset
res = test_date - offset

# printing result
print("Last business day : " + str(res))

Output : 

The original date is : 2020-02-03 00:00:00
Last business day : 2020-01-31 00:00:00