Python program to get the nth weekday after a given date

Given a date and weekday index, the task is to write a Python program to get the date for the given day of the week occurring after the given date. The weekday index is based on the below table:

Index	Weekday
0	Monday
1	Tuesday
2	Wednesday
3	Thursday
4	Friday
5	Saturday
6	Sunday

Examples:

Input : test_date = datetime.datetime(2017, 3, 14), weekday_idx = 4

Output : 2017-03-17 

Explanation : 14 March is Tuesday, i.e 1 weekday, 4th weekday is a Friday, i.e 17 March.

Input : test_date = datetime.datetime(2017, 3, 12), weekday_idx = 5

Output : 2017-03-18

Explanation : 12 March is Sunday, i.e 6th weekday, 5th weekday in next week is a Saturday, i.e 18 March.

Method #1 : Using timedelta() + weekday()

In this, we subtract the date weekday from the weekday index and then check for required index extracted, then the required day, if negative is summed with 7 and then the resultant number is added to current date using timedelta().

Python3

# Python3 code to demonstrate working of
# Next weekday from Date
# Using timedelta() + weekday()
import datetime

# initializing dates
test_date = datetime.datetime(2017, 3, 14)

# printing original date
print("The original date is : " + str(test_date)[:10])

# initializing weekday index
weekday_idx = 4

# computing delta days
days_delta = weekday_idx - test_date.weekday()
if days_delta <= 0:
    days_delta += 7

# adding days to required result
res = test_date + datetime.timedelta(days_delta)

# printing result
print("Next date of required weekday : " + str(res)[:10])

Output:

The original date is : 2017-03-14
Next date of required weekday : 2017-03-17

Method #2 : Using lambda function

Using the lambda function provides a shorthand and compact solution to the question. 

Python3

# Python3 code to demonstrate working of
# Next weekday from Date
# Using lambda function
import datetime

# initializing dates
test_date = datetime.datetime(2017, 3, 14)

# printing original date
print("The original date is : " + str(test_date)[:10])

# initializing weekday index
weekday_idx = 4

# lambda function provides one liner shorthand
def lfnc(test_date, weekday_idx): return test_date + \
    datetime.timedelta(days=(weekday_idx - test_date.weekday() + 7) % 7)


res = lfnc(test_date, weekday_idx)

# printing result
print("Next date of required weekday : " + str(res)[:10])

Output:

The original date is : 2017-03-14
Next date of required weekday : 2017-03-17