python loop x + 1 times in a list of list until number y
<p>What I want is the list in <code>num</code> loops <code>x + 1</code> everytime until <code>y</code> is generated(and loops is stoped), which is a large number.</p>

<pre><code>def loop_num(y):
    num = []
    num.append([1])
    num.append([2,3])
    num.append([4,5,6]) 
    num.append([7,8,9,10]) 
    ... #stop append when y in the appended list
    #if y = 9, then `append [7,8]` and `return num`
    return num


# something like[[1 item], [2items], [3items], ...]
# the number append to the list can be a random number or ascending integers. 
</code></pre>

<p>sorry for not clear</p>

<p>Two <a href="https://docs.python.org/2/library/itertools.html#itertools.count" rel="nofollow"><code>itertools.count</code></a> objects should do what you want:</p>

<pre><code>from itertools import count

def loop_num(y):
    counter, x = count(1), count(1)
    n = 0
    while n &lt; y:
        num = []
        for i in range(next(x)):
            num.append(next(counter))
            if num[-1] == y:
                break
        yield num
        n = num[-1]
</code></pre>

<p>Output:</p>

<pre><code>&gt;&gt;&gt; list(loop_num(100))
[[1],
 [2, 3],
 [4, 5, 6],
 [7, 8, 9, 10],
 [11, 12, 13, 14, 15],
 [16, 17, 18, 19, 20, 21],
 [22, 23, 24, 25, 26, 27, 28],
 [29, 30, 31, 32, 33, 34, 35, 36],
 [37, 38, 39, 40, 41, 42, 43, 44, 45],
 [46, 47, 48, 49, 50, 51, 52, 53, 54, 55],
 [56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66],
 [67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78],
 [79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91],
 [92, 93, 94, 95, 96, 97, 98, 99, 100]]
</code></pre>

python list loops random iteratee