Given a list of dates, the task is to write a Python program to check if all the dates are consecutive in the list.
Input : [datetime(2019, 12, 30), datetime(2019, 12, 31), datetime(2020, 1, 1), datetime(2020, 1, 2), datetime(2020, 1, 3), datetime(2020, 1, 4)]
Output : True
Explanation : All dates are consecutive, from 30 Dec 2019 to 4 January 2020.
Input : [datetime(2019, 12, 29), datetime(2019, 12, 31), datetime(2020, 1, 1), datetime(2020, 1, 2), datetime(2020, 1, 3), datetime(2020, 1, 4)]
Output : False
Explanation : Non consecutive dates.
Method #1 : Using days() + loop
In this, we check consecutive dates by checking days difference from the previous date using days(). The iteration of all dates is done using a loop.
Python3
# Python3 code to demonstrate working of# Test if dates are consecutive# Using days() + loopfrom datetime import datetime, timedelta# initializing listtest_list = [datetime(2019, 12, 30), datetime(2019, 12, 31), datetime(2020, 1, 1), datetime(2020, 1, 2), datetime(2020, 1, 3), datetime(2020, 1, 4)]# printing original listprint("The original list is : " + str(test_list))# using loop for iterating all elementsres = Truefor idx in range(1, len(test_list)): # checking for 1 day time difference if (test_list[idx] - test_list[idx - 1]).days != 1: res = False break# printing resultprint("Are dates consecutive : " + str(res)) |
Output:
The original list is : [datetime.datetime(2019, 12, 30, 0, 0), datetime.datetime(2019, 12, 31, 0, 0), datetime.datetime(2020, 1, 1, 0, 0), datetime.datetime(2020, 1, 2, 0, 0), datetime.datetime(2020, 1, 3, 0, 0), datetime.datetime(2020, 1, 4, 0, 0)]
Are dates consecutive : True
Time Complexity : O(n)
Space Complexity : O(1)
Method #2 : Using all() + days()
Similar to the above method, the only difference here is all() is used to check for each day consecution for a more compact solution.
Python3
# Python3 code to demonstrate working of# Test if dates are consecutive# Using all() + days()from datetime import datetime, timedelta# initializing listtest_list = [datetime(2019, 12, 30), datetime(2019, 12, 31), datetime(2020, 1, 1), datetime(2020, 1, 2), datetime(2020, 1, 3), datetime(2020, 1, 4)]# printing original listprint("The original list is : " + str(test_list))# using loop for iterating all elementsres = all((test_list[idx] - test_list[idx - 1]).days == 1 for idx in range(1, len(test_list)))# printing resultprint("Are dates consecutive : " + str(res)) |
Output:
The original list is : [datetime.datetime(2019, 12, 30, 0, 0), datetime.datetime(2019, 12, 31, 0, 0), datetime.datetime(2020, 1, 1, 0, 0), datetime.datetime(2020, 1, 2, 0, 0), datetime.datetime(2020, 1, 3, 0, 0), datetime.datetime(2020, 1, 4, 0, 0)]
Are dates consecutive : True
Time Complexity : O(n)
Space Complexity : O(1)
Method #3: Using set()
- Initialize a new list named ‘date_range‘ containing all dates from the first date in the ‘test_list‘ to the last date in the ‘test_list‘. To do this, use the date range function and add the time delta of one day to each date.
- Check if ‘date_range‘ and ‘test_list‘ contain the same dates by converting both lists to sets and comparing them. If they are the same, then the dates in ‘test_list‘ are consecutive.
- Return True if the dates are consecutive and False otherwise.
Python3
from datetime import datetime, timedelta# initializing listtest_list = [datetime(2019, 12, 30), datetime(2019, 12, 31), datetime(2020, 1, 1), datetime(2020, 1, 2), datetime(2020, 1, 3), datetime(2020, 1, 4)]# printing original listprint("The original list is : " + str(test_list))# using set() to check for consecutive datesdate_range = [test_list[0] + timedelta(days=x) for x in range((test_list[-1]-test_list[0]).days + 1)]res = set(test_list) == set(date_range)# printing resultprint("Are dates consecutive : " + str(res)) |
The original list is : [datetime.datetime(2019, 12, 30, 0, 0), datetime.datetime(2019, 12, 31, 0, 0), datetime.datetime(2020, 1, 1, 0, 0), datetime.datetime(2020, 1, 2, 0, 0), datetime.datetime(2020, 1, 3, 0, 0), datetime.datetime(2020, 1, 4, 0, 0)] Are dates consecutive : True
Time Complexity: O(n) – linear time complexity since we loop through the test_list and the date_range only once
Auxiliary Space: O(n) – linear space complexity since we create a new list, ‘date_range’, containing all dates in the given range
