title: Creating an increasing list in Python
body: <p>I am trying to create some lists from other lists putting some conditions along the way. I want to write these lists finally into a csv. Here is the code which I attempted.</p>
  
  <pre><code>x = [None]*1000
  y = [None]*1000
  z = [None]*1000
  i = 0 
  for d in range(0,len(productID)):
      for j in range(0,len(productID[d])):
          if productID[d][j].startswith(u'sku'):
  
              x[i] = map[productID[d][j]]
              y[i] = name[d]
              z[i] = priceID[d][productID[d][j]].get(u'e')
  
              i = i + 1  
  
  plan_name = x[0:i]
  dev_name  = y[0:i]
  dev_price = z[0:i]
  </code></pre>
  
  <p>This is working fine, but I assume there should be a better way of doing this. Can anyone suggest how can I create a list while looping without having to define it first?</p>