product of lists, not necessarily all the lists at the same time
<p>I have three lists (L1, L2, L3), something like :</p>

<pre><code>L1 = [1,2]
L2 = ['a','b']
L3 = ['A','B']
</code></pre>

<p>I want to compute the product of L1*L2*L3, id est,</p>

<pre><code>itertools.product(L1,L2,L3) = [ [1,'a','A'], [1,'a','B'], ... ]
</code></pre>

<p>but I want to take or not in account some lists; hence,[1,], [ 1, 'a' ] would be a part of the result, like ['a',], ['a', 'B'] and so on.</p>

<p>Any idea to help me ? Thanks !</p>
