title: ValueError: cannot switch from manual field specification to automatic field numbering
body: <p>The class:</p>
  
  <pre><code>class Book(object):
      def __init__(self, title, author):
          self.title = title
          self.author = author
  
      def get_entry(self):
          return "{0} by {1} on {}".format(self.title, self.author, self.press)
  </code></pre>
  
  <p>Create an instance of my book from it:</p>
  
  <pre><code>In [72]: mybook = Book('HTML','Lee')
  In [75]: mybook.title
  Out[75]: 'HTML'
  In [76]: mybook.author
  Out[76]: 'Lee'
  </code></pre>
  
  <p>Please notice that I didn't initialize attribute 'self.press',while use it in the get_entry method.Go ahead to type in data.</p>
  
  <pre><code>mybook.press = 'Murach'
  mybook.price = 'download'
  </code></pre>
  
  <p>Till now, I can specify all the data input with <code>vars</code></p>
  
  <pre><code>In [77]: vars(mybook)
  Out[77]: {'author': 'Lee', 'title': 'HTML',...}
  </code></pre>
  
  <p>I hardtype lot of data about mybook in the console.When try to call get_entry method, errors report.</p>
  
  <pre><code>mybook.get_entry()
  ValueError: cannot switch from manual field specification to automatic field numbering.
  </code></pre>
  
  <p>All this going in interactive mode on console.I cherish the data inputed, further to pickle <code>mybook</code> object in file. However, it is flawed. How can rescue it in the interactive mode.
  or I have to restart all over again.</p>