Separate and merge overlapping dates in list of dicts

Question

Working in Python, I've got a list of dicts containing a start date, end date and a list of values.

These may overlap and I need to break them into unique time periods, and merge the values from any overlapping period.

For example:

[
    # Cover the space of 1 year
    {
        "values": ["a", "b", "c"],
        "start": "2023-01-01T00:00:00+00:00",
        "end": "2024-01-01T00:00:00+00:00",
    },
    # Overlapping month with new values
    {
        "values": ["d", "e"],
        "start": "2023-02-01T00:00:00+00:00",
        "end": "2023-03-01T00:00:00+00:00",
    },
]

Should output:

[
    {
        "values": ["a", "b", "c"],
        "start": "2023-01-01T00:00:00+00:00",
        "end": "2023-02-01T00:00:00+00:00",
    },
    {
        "values": ["a", "b", "c", "d", "e"],
        "start": "2023-02-01T00:00:00+00:00",
        "end": "2022-03-01T00:00:00+00:00",
    },
    {
        "values": ["d", "e"],
        "start": "2023-03-01T00:00:00+00:00",
        "end": "2024-01-01T00:00:00+00:00",
    },
]

I've been able to merge all the dates down to a single date range of the min/max, but I'm completely stumped on how I can dynamically work out the overlapping values.

Saxtheowl · Accepted Answer · 2023-04-17 19:44:12Z

0

Just sort the list by start date and then iterating through the sorted list to find and merge overlapping periods and you will obtain the desired result.

edit: if you also want to keep track of the time windows during which these values are active we can modify our code like this:

def merge_overlapping_dates(input_list: List[Dict]) -> List[Dict]:
    # Sort the list by start date
    input_list.sort(key=lambda x: parse_date(x["start"]))

    result = []
    for item in input_list:
        # Parse dates
        start = parse_date(item["start"])
        end = parse_date(item["end"])

        # Check if the current item overlaps with the previous item in the result
        if result and start <= parse_date(result[-1]["end"]):
            # Merge overlapping values
            result[-1]["values"].extend(item["values"])
            result[-1]["values"] = list(set(result[-1]["values"]))

            # Update the time window
            if end > parse_date(result[-1]["end"]):
                old_end = result[-1]["end"]
                result[-1]["end"] = item["end"]
                result[-1]["time_windows"].append({"start": old_end, "end": item["end"]})
        else:
            # Add a new item to the result
            result.append({"values": item["values"], "start": item["start"], "end": item["end"], "time_windows": [{"start": item["start"], "end": item["end"]}]})

    return result

edited Apr 17, 2023 at 19:44

answered Apr 17, 2023 at 19:23

Saxtheowl

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1 Comment

TKems Over a year ago

This is sort of what I've got at the moment, problem is it merges everything together as a whole.. rather than separting it out into time windows.

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