title: pandas: cannot do positional indexing on DatetimeIndex with these indexers [2016-08-01 00:00:00] of Timestamp
body: <p>I a newbie using pandas, I am trying to access my (date indexed) dataframe <code>df</code> using code similar to this:</p>
  
  <pre><code>for idx, row in df.iterrows():
      if idx &lt; startrow:
          continue
  
      col1_data = df.iloc[idx]['col1']
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code>cannot do positional indexing on &lt;class 'pandas.core.indexes.datetimes.DatetimeIndex'&gt; with these indexers [2016-08-01 00:00:00] of &lt;class 'pandas._libs.tslib.Timestamp'&gt;
  </code></pre>
  
  <p>How do I fix this ?</p>