title: How to sum previous rows in a dataframe?
body: <p>I'm not sure how to correctly word what I want to do, or if this is even possible, so sorry if this sounds confusing and doesn't make sense. What I want to do basically is some way to create a separate column in a dataframe that sums consecutive values. For instance, I have this column, shown below, and I would like a separate column, which contains the sum of 0.00871 and 0.001, and then 0.000603 and 0.0123, and 0.000871 and 4.37E-05, and etc. Does this make sense? If so, is there a way I can code for this, instead of doing it manually? All help is appreciated! I would prefer to do this on Python, but any language would suffice.</p>
  <p><a href="https://i.stack.imgur.com/fp8b8.png" rel="nofollow noreferrer">Not allowed to embed the image, so hopefully this works</a></p>