title: Assign a whole row as None: IndexError: tuple index out of range
body: <p>Create a new dataframe.</p>
  
  <pre><code>df = pd.DataFrame([[1, 2], [4, 6], [7, 8]],
       index=['cobra', 'viper', 'sidewinder'],
       columns=['max_speed', 'shield']) df
  </code></pre>
  
  <p>Show it's value:</p>
  
  <pre><code>df
              max_speed  shield
  cobra               1       2
  viper               4       6
  sidewinder          7       8
  </code></pre>
  
  <p>Now i want to assign the whole first row as <code>10</code>.</p>
  
  <pre><code>df.iloc[0:1,] = 10
  df
              max_speed  shield
  cobra              10      10
  viper               4       6
  sidewinder          7       8
  </code></pre>
  
  <p>Assign the whole first row as <code>None</code>.</p>
  
  <pre><code>df.iloc[0:1,] = None
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
    File "/usr/local/lib/python3.5/dist-packages/pandas/core/indexing.py", line 190, in __setitem__
      self._setitem_with_indexer(indexer, value)
    File "/usr/local/lib/python3.5/dist-packages/pandas/core/indexing.py", line 471, in _setitem_with_indexer
      info_idx = indexer[info_axis]
  IndexError: tuple index out of range
  </code></pre>
  
  <p>Why can't assign a whole row as None with just one expression?  </p>
  
  <pre><code>df.iloc[0,0] = None
  df.iloc[0,1] = None
  </code></pre>
  
  <p>The two statements can assign the row as <code>None</code>,why can't write only one expression such as <code>df.iloc[0:1,] = 10</code>?</p>