日付処理

from datetime import datetime
from dateutil.relativedelta import relativedelta

# 日単位でのイテレート ------------------------------------
# 補助関数
def _generate_between_date(start_date_str, stop_date_str):
    start_date = datetime.strptime(start_date_str, '%Y%m%d')
    stop_date = datetime.strptime(stop_date_str, '%Y%m%d')
    while start_date <= stop_date:
        yield start_date.strftime('%Y%m%d')
        start_date += relativedelta(days=1)

# こちらを使う
def date_sequence_generator(dates_str):
    for date_str in dates_str.split(','):
        if '-' in date_str:
            for date in _generate_between_date(*date_str.split('-')):
                yield date
        else:
            yield date_str


# 月単位でのイテレート -----------------------------------
def _generate_between_month(start_month_str, stop_month_str):
    start_month = datetime.strptime(start_month_str, '%Y%m')
    stop_month = datetime.strptime(stop_month_str, '%Y%m')
    while start_month <= stop_month:
        yield start_month.strftime('%Y%m')
        start_month += relativedelta(months=1)

def month_sequence_generator(months_str):
    for month_str in months_str.split(','):
        if '-' in month_str:
            for month in _generate_between_month(*month_str.split('-')):
                yield month
        else:
            yield month_str

use DateTime;

class DateIterator
{
    function iterateDate($target_dates)
    {
        $comma_explodeds = explode(',', $target_dates);
        foreach ($comma_explodeds as $cma) {
            $hyphen_explodeds = explode('-', $cma);
            if (count($hyphen_explodeds) === 1) {
                yield $cma;
            } elseif (count($hyphen_explodeds) === 2) {
                $d = DateTime::createFromFormat(
                    'Ymd', $hyphen_explodeds[0]);
                $t = DateTime::createFromFormat(
                    'Ymd', $hyphen_explodeds[1]);
                if ($d === false || $t === false) {
                    throw new \UnexpectedValueException(
                        'iterateDate parse date');
                }
                while ($d <= $t) {
                    yield $d->format('Ymd');
                    $d->modify('+1 day');
                }
            } else {
                throw new \UnexpectedValueException(
                    'iterateDate hyphen');
            }
        }
    }
}

KotlinではGeneratorの機能がまだexperimentalなので、Listを返すようにする。

• Coroutines - Kotlin Programming Language

また、Java8より導入されたLocalDateTimeを利用する。

import java.time.LocalDate
import java.time.format.DateTimeFormatter
import java.time.format.ResolverStyle

fun String.iterateDate(): List<String> {

    val formatter = DateTimeFormatter.ofPattern("uuuuMMdd").withResolverStyle(ResolverStyle.STRICT)
    val dateList = mutableListOf<String>()

    this.split(',').forEach {

        val hyphenSplit = it.split('-')

        when (hyphenSplit.size) {
            1 -> {
                // パースできるかだけ確認
                LocalDate.parse(hyphenSplit[0], formatter)
                dateList += hyphenSplit[0]
            }
            2 -> {
                var curDate = LocalDate.parse(hyphenSplit[0], formatter)
                val tgtDate = LocalDate.parse(hyphenSplit[1], formatter)
                while (curDate <= tgtDate) {
                    dateList += curDate.format(formatter)
                    curDate = curDate.plusDays(1)
                }
            }
            else -> {
                throw IllegalArgumentException("Can't iterate date: %s".format(it))
            }
        }
    }
    return dateList
}