title: Pandas - create dataframe manually and insert values
body: <p>Here is my code:</p>
  
  <pre><code>import pandas as pd
  df = pd.DataFrame(columns = ["A", "B"])
  df.iloc[0]['A'] = 5
  </code></pre>
  
  <p>Here is output:</p>
  
  <pre><code>Traceback (most recent call last):
    File "K:/Dop/Pentas/Simpletest/Temp.py", line 38, in &lt;module&gt;
      df.iloc[0]['A'] = 5
    File "C:\Python34\lib\site-packages\pandas\core\indexing.py", line 1189, in __getitem__
      return self._getitem_axis(key, axis=0)
    File "C:\Python34\lib\site-packages\pandas\core\indexing.py", line 1480, in _getitem_axis
      return self._get_loc(key, axis=axis)
    File "C:\Python34\lib\site-packages\pandas\core\indexing.py", line 89, in _get_loc
      return self.obj._ixs(key, axis=axis)
    File "C:\Python34\lib\site-packages\pandas\core\frame.py", line 1719, in _ixs
      label = self.index[i]
    File "C:\Python34\lib\site-packages\pandas\core\index.py", line 1076, in __getitem__
      return getitem(key)
  IndexError: index 0 is out of bounds for axis 0 with size 0
  </code></pre>
  
  <p>Any suggestions on how to fix it? I do not know overall size of my dataframe before hand, but I can guess.</p>