Removing dates within 'n' days of each other in Dictionaries-CodePudding

I have a dictionary where the values of the dictionary are lists of dates. For each key, if, in the list of dates, there are dates within 30 days (or more generally n days) of each other, I only want to take the last listed date.

For example, I have a dictionary as follows:

a : ['2020-12-11'] 
b : ['2020-05-30', '2022-09-11'] 
c : ['2021-07-28', '2022-07-20', '2022-07-07', '2022-06-30'] 
d : ['2022-04-17', '2022-04-18', '2022-04-15', '2022-08-20']

Now, since I only want to take the last listed date within the 30 day period for each value, I'm trying to get the following output:

a : ['2020-12-11'] 
b : ['2020-05-30', '2022-09-11'] 
c : ['2021-07-28', '2022-06-30'] 
d : ['2022-04-15', '2022-08-20']

The output value does not change for a or b since there are no dates within 30 days range of each other. The output value for c changes since 2022-07-20, 2022-07-07, and 2022-06-30 are within 30 days of each other, and since 2022-06-30 is listed last it is kept in the list (despite 2022-07-20 being at a later date). For d, the same thing should happen - 2022-04-17, 2022-04-18, 2022-04-15 are all within 30 days of each other, but 2022-04-15 is listed last so we want that, while 2022-08-20 is more than 30 days away so it's kept in too.

If anyone knows how to help me with this problem I would greatly appreciate it since I'm not sure how to approach it, especially in a computationally fast way. Moreover, how can this be generalized to make it 60 days, 100 days etc.? Thank you!

CodePudding user response：

Just loop through the dict, then loop through inner list, transform values to datetime and compare them with last value in inner list

test_dict = {
    "a" : ['2020-12-11'],
    "b" : ['2020-05-30', '2022-09-11'] ,
    "c" : ['2021-07-28', '2022-07-20', '2022-07-07', '2022-06-30'] ,
    "d" : ['2022-04-17', '2022-04-18', '2022-04-15', '2022-08-20'],
}


from datetime import datetime, timedelta
def only_leave_last_date(d: dict, days_gap:int) -> dict:
    new_dict = {}
    for key, value in d.items():
        if not value:            
            new_value_str = []
        else:
            new_value_dt = [datetime.strptime(value[0], '%Y-%m-%d')]
            new_value_str = [value[0]]
            for date_str in value[1:]:
                date = datetime.strptime(date_str, '%Y-%m-%d')
                if abs(date - new_value_dt[-1]) <= timedelta(days=days_gap):
                    new_value_dt[-1] = date
                    new_value_str[-1] = date_str
                else:
                    new_value_dt.append(date)
                    new_value_str.append(date_str)
        new_dict[key] = new_value_str
    return new_dict

only_leave_last_date(test_dict, days_gap=30)

Output:

{'a': ['2020-12-11'],
 'b': ['2020-05-30', '2022-09-11'],
 'c': ['2021-07-28', '2022-06-30'],
 'd': ['2022-04-15', '2022-08-20']}