title: pop() method in python lists doesn't work properly
body: <p>When I execute the following code in Python 2.7.3:</p>
  
  <pre><code>#!/usr/bin/env python
  # -*- coding: utf-8 -*-
  
  
  class A(object):
      def __init__(self):
          self.s = []
  
  
  class B(object):
      def __init__(self):
          self.a = A()
  
  
  class C(object):
      def __init__(self):
          self.b = B()
  
  
  c = C()
  
  print c.b.a.s
  
  c.b.a.s.append(1)
  c.b.a.s.append(2)
  c.b.a.s.append(3)
  c.b.a.s.append(4)
  c.b.a.s.append(5)
  
  print c.b.a.s
  
  for element in c.b.a.s:
      print c.b.a.s.pop()
  
  print c.b.a.s
  </code></pre>
  
  <p>I get the output:</p>
  
  <pre><code>[]
  [1, 2, 3, 4, 5]
  5
  4
  3
  [1, 2]
  </code></pre>
  
  <p>But I expect the for statement pop all the elements in the list and leave c.b.a.s as [].</p>
  
  <p><strong>The question:</strong>
  I omit something in the code or is something wrong in pop() method?</p>