Генераторы

from itertools import count
 
def gen_stream(n, seq, extractor=lambda x: x):
    seq = dict(map(extractor, seq))
    iterable = count() if n is None else range(n)
    for i in iterable:
        yield seq.get(i, 0)

class DictIterator(object):
    def __init__(self, dict_gen):
        self.dg = dict_gen
        self.cursor = -1
 
    def __next__(self):
        self.cursor += 1
        return self.dg[self.cursor]
 
    def __iter__(self):
        return self
 
 
class DictGen(object):
    def __init__(self, limit, tuples):
        self._dict = dict(tuples)
        self.limit = limit
 
    def __getitem__(self, item):
        if item >= self.limit:
            raise StopIteration
 
        return self._dict.get(item, 0)
 
    def __len__(self):
        return self.limit
 
    def __iter__(self):
        return DictIterator(self)
 
 
dg = DictGen(10, [(4, 9), (7, 12)])
for itm in dg:
    print(itm)

from itertools import count
def gen_stream(total, sorted_iterable, extractor=lambda x: x):
    sorted_iterable = dict(map(extractor, sorted_iterable))
    iterable = count() if total is None else range(total)
    for i in iterable:
        yield sorted_iterable.get(i, 0)
#gen = gen_stream(9,[(4,111),(7,12)])
#list(gen)
def day_extractor(x):
    months = [31,28,31,30,31,31,30,31,30,31,30,31]
    acc = sum(months[:x[1]-1]) + x[0] - 1
    return (acc, x[2])
#precipitation_days = [(3,1,4),(5,2,6)]
#list(gen_stream(59,precipitation_days,day_extractor))

sorted_iterable = dict(map(extractor, sorted_iterable))