title: Environment: Python(3.6.4), how come the value(level) is different?
body: <p>Hard to describe it, ref below codes, pls</p>
  
  <p>For the var item1, I wonder:</p>
  
  <p>Section1, item1's value is an element of lst, a tuple.
  but from Section2, items1's value goes to next level, is an element of an element of lst.</p>
  
  <h2>how to understand this?</h2>
  
  <pre><code> import random
  
   lst1 = [random.randint(1, 100) for i in range(10)]
   lst2 = [random.randint(1, 100) for i in range(10)]
   lst = list(zip(lst1, lst2))
  
   print(lst)
  
   # section 1
   for item1 in lst:
       print(item1)
  
   # section 2
   for item1, item2 in lst:
       print(item1, item2)
  </code></pre>
  
  <hr>
  
  <p>output example:</p>
  
  <pre><code>[(34, 85), (9, 18), (56, 89), (69, 82), (21, 69), (21, 46), (39, 78), (19, 27), (33, 71), (94, 2)]
  </code></pre>
  
  <p>section1:</p>
  
  <pre><code>(34, 85)
  ...
  (94, 2)
  </code></pre>
  
  <p>section2:</p>
  
  <pre><code>34 85
  ...
  94 2
  </code></pre>
  
  <hr>
  
  <p>how come from section1 item1 = (34, 85) but item1 just = 34 from section2</p>