title: loading a text file of multiple columns but different rows in python
body: <p>I have a text file with three columns and 280 rows for columns 1 and 2, but the third column is only 10 rows (i.e. I only have data for a certain number of rows). When I try to plot columns 2 and 3 against column 1 it complains that column 3 does not have enough data for example.</p>
  <p>col1 col2 col3
  10     3    4
  20     7    -
  30    12    7
  40     2    -
  50    22    3.5
  60    11    -
  70    43    -
  .
  .</p>
  <p>Is there a way to go around this?
  Thanks in advance</p>