title: dict comprehension failure - not enough values to unpack
body: <p>I want to create a dict from a list of strings:</p>
  
  <pre><code>print(l)
  print(l[0])                            # 1st string in list
  print(l[0].split(',',1))
  print(len(l[0].split(',',1)))
  d = {int(k):v for k,v in l[0].split(',',1)}
  
  ['0,[7,2,5,7]', '1,[7,18,6,2]']
  0,[7,2,5,7]
  ['0', '[7,2,5,7]']
  2
  </code></pre>
  
  <p>However, I get <code>d = {int(k):v for k,v in l[0].split(',',1)}     ValueError: not enough values to unpack (expected 2, got 1)</code></p>
  
  <p>I can't understand why, as <code>l[0].split(',',1)</code> returns 2 values, as can be seen from my previous checks (<code>print(len(l[0].split(',',1)))</code> returns 2)</p>
  
  <p><em>My desired output:</em></p>
  
  <pre><code>d = {0 : [7,2,5,7]}
  </code></pre>