from itertools import chain, repeat

def interleave(iterables, repeat_rates=None):
    if repeat_rates is not None and len(iterables) != len(repeat_rates):
        raise ValueError('repeat_rates must be either None or be same length with iterables')

    iterators = []
    for i, iterable in enumerate(iterables):
        if repeat_rates:
            rate = repeat_rates[i]
            if rate > 1:
                iterable = chain.from_iterable(repeat(iterable, rate))
        iterators.append(iter(iterable))

    for item in chain.from_iterable(zip(*iterators)):
        yield item