class ParseRange:
    def __init__(self, ranges_string):
        self.ranges_string = ranges_string
        self.numbers = []
        self.ranges = self.ranges_string.split(',')

    def parse_ranges(self):
        for r in self.ranges:
            start, end = map(int, r.split('-'))
            self.numbers.extend(range(start, end + 1))
        return self.numbers


parser = ParseRange('1-2,8-15,23-25')
print(parser.parse_ranges())

parser = ParseRange('0-0, 4-8, 20-20, 43-45')
print(parser.parse_ranges())