title: Progress bar with tqdm while iterating over the items in a python dictionary
body: <p>If I'm trying to get a progress bar while iterating over a dict, how can I do this with tqdm? I'm using Python 2.7.</p>
  
  <p>This works great with lists:</p>
  
  <pre><code>for i in tdqm(l, len(l):
      &lt;do stuff&gt;   
  </code></pre>
  
  <p>But fails over dicts:</p>
  
  <pre><code>for k, v in tqdm(d.items(), len(d)):
     &lt;do stuff&gt;
  </code></pre>
  
  <p>What's the proper way to do this with dicts?</p>
  
  <p>Here's a real example:</p>
  
  <pre><code>d = {'k1':1, 'k2':2}
  for k, v in tqdm(d.items(), len(d)):
      print 'foo'
      a = 1 + 100
      print 'bar'
  </code></pre>
  
  <p>I get:</p>
  
  <pre><code>-------------------------------------------------------------------
  TypeError                         Traceback (most recent call last)
  &lt;ipython-input-30-7e4ce2b85414&gt; in &lt;module&gt;()
        1 d = {'k1':1, 'k2':2}
  ----&gt; 2 for k, v in tqdm(d.items(), len(d)):
        3     print 'oasdlkfj'
        4     a = 1 + 100
        5     print 'y'
  
  /home/monica/anaconda2/envs/pytorch_p27/lib/python2.7/site-packages/tqdm/_tqdm.pyc in __init__(self, iterable, desc, total, leave, file, ncols, mininterval, maxinterval, miniters, ascii, disable, unit, unit_scale, dynamic_ncols, smoothing, bar_format, initial, position, postfix, unit_divisor, gui, **kwargs)
      810                 if self.pos:
      811                     self.moveto(self.pos)
  --&gt; 812                 self.sp(self.__repr__(elapsed=0))
      813                 if self.pos:
      814                     self.moveto(-self.pos)
  
  /home/monica/anaconda2/envs/pytorch_p27/lib/python2.7/site-packages/tqdm/_tqdm.pyc in __repr__(self, elapsed)
      842             self.desc, self.ascii, self.unit,
      843             self.unit_scale, 1 / self.avg_time if self.avg_time else None,
  --&gt; 844             self.bar_format, self.postfix, self.unit_divisor)
      845 
      846     def __lt__(self, other):
  
  /home/monica/anaconda2/envs/pytorch_p27/lib/python2.7/site-packages/tqdm/_tqdm.pyc in format_meter(n, total, elapsed, ncols, prefix, ascii, unit, unit_scale, rate, bar_format, postfix, unit_divisor)
      288             if prefix:
      289                 # old prefix setup work around
  --&gt; 290                 bool_prefix_colon_already = (prefix[-2:] == ": ")
      291                 l_bar = prefix if bool_prefix_colon_already else prefix + ": "
      292             else:
  
  TypeError: 'int' object has no attribute '__getitem__'
  </code></pre>