title: Pandas itertuple returns inconsistent type, either Pandas or tuple
body: <p>I am getting a strange behavior that I have never seen before from my code that I have used many times before on smaller datasets. I am parsing VCF files with Pandas dataframe read_table. VCF files have a header and then 9 columns + however many columns of individuals. Before when I used <code>for row in genomes_df.itertuples():</code> to iterate through each row of the dataframe I could call a column, "SVLEN", with <code>row.SVLEN</code>. When I check <code>type(row)</code> it is a Pandas object. Today I ran my script on a larger file (350 columns vs 10 columns previously) of same VCF format, it is giving me <code>AttributeError: 'tuple' object has no attribute 'SVLEN'</code> because now <code>type(row)</code> is a tuple!</p>
  
  <p>What is going on here? The column names are different (<code>NWD107911.mark_dupes</code> vs <code>NWD107911</code>)  but I checked that there are no spaces in the names (read in another post that it could cause different behavior).</p>