import io


def iter_words(stream, bufsize=32):
    if not isinstance(stream, io.IOBase):
        stream = io.StringIO(stream)
    word = ""

    while True:
        buf = stream.read(bufsize)
        if not buf:
            if word:
                yield word
            break
        for ch in buf:
            if ch == " ":
                if word:
                    yield word
                    word = ""
            else:
                word += ch


def freq(s, bufsize):
    words = {}
    for word in iter_words(s, bufsize):
        if word in words:
            words[word] += 1
        else:
            words[word] = 1
    words = list(words.items())
    words.sort(key=lambda el: el[1])
    return words


chars = "qwertyuiopasdfghjklzxcvbnm"
words = [c * i for c in chars for i in range(1, 20)]
data = " q " + "%s " % " ".join(words) * 10


if __name__ == "__main__":
    res = freq(data, 64)
    print(res)
    assert res[-1][0] == "q"