Grouping Consecutive Dates Together

I have a list of (many) employees in Excel/csv who take sick days, listed in the following format. Each sick day instance gets it's own line. I want to add another column 'Result',

Solution 1:

defgroup(iterable):
    myIter = iter(iterable)

    run = [next(myIter)]
    defcontinuesRun(x):
        return run[-1]==x-1for x in myIter:
        if continuesRun(x):
            run.append(x)
        else:
            yield run
            run = [x]
    yield run

Demo:

>>> list( group([1,10,11,12,20,21]) )
[[1], [10, 11, 12], [20, 21]]

To apply this to your situation, define the function continuesRun like so, in pseudocode:

def continuesRun(date):
    previousDate = run[-1]
    return previousDate==date-1dayor (previousDate.weekday==Friday and previousDate==date-3day)

sidenote: It seems slightly morally/pragmatically wrong, in my personal opinion, to count sickdays spans bordering weekends as potentially 2 or 4 days longer. But if you have good reason to do so, who am I to judge. =) To count those, post-process your runs: add 2 if the first day was Monday, and add 2 if the last day was Friday, then add len(d for d in range(run[-1]-run[0]) if (run[0]+d*day).isWeekend()). Of course this does not count holidays, in which case you would do .isHoliday() or .isWeekend() and make the "add 2" logic exactly like the len(...) logic, by iterating back until you find a non-holiday, and penalizing the person for each holiday-or-weekend thus adjacent to the run.