How do I find missing dates in a list of sorted dates?

Question

In Python how do I find all the missing days in a sorted list of dates?

Answer 1

A good way of getting this done in Python is as follows. You need not worry about efficiency unless you have dates from multiple years in your list and this code always needs to run as per user interaction and yield output immediately.

1. Get missing dates from one list (sorted or not)

Create a function that gives you all the dates from start_date to end_date. And use it.

import datetime

def get_dates(start_date, end_date):
    span_between_dates = range(end_date - start_date).days
    for index in span_between_dates + 1:
        # +1 is to make start and end dates inclusive.
        yield start_date + datetime.timedelta(index)

my_date_list = ['2017-03-05', '2017-03_07', ...]
# Edit my_date_list as per your requirement.
start_date = min(my_date_list)
end_date = max(my_date_list)
for current_date in get_dates(start_date, end_date)
    if date not in my_date_list:
        print date

2. Get missing or overlapping dates between two date ranges.

get_dates function should be defined.

my_other_date_list = []  # your other date range
start_date = min(my_date_list)
end_date = max(my_date_list)
for current_date in get_dates(start_date, end_date)
    if (date in my_date_range) and (date in my_other_date_list):
        print ('overlapping dates between 2 lists:')
        print date
    elif (date in my_date_range) and (date not in my_other_date_list):
        print ('missing dates:')
        print date