title: what kind of statement before for loop is possible in python
body: <p>I see a code like this in python</p>
  
  <pre><code>x = [[0] * 2 for i in range(2)]
  </code></pre>
  
  <p>this results in an array of 2d array. x has a value of</p>
  
  <pre><code>[[0, 0], [0, 0]]
  </code></pre>
  
  <p>My question is what kind of statement  can we put in front of the for loop? I don't quite understand how to use this. Is there a name for this kind of use in python? Is this a good practice(pythonic)?</p>