title: How to iterate over latitude longitude values of a grib2 file?
body: <p>I'm trying to get the <code>uvIndex</code> of all the lat,lng present in a grib2 file.
  This is the <a href="ftp://ftpprd.ncep.noaa.gov/pub/data/nccf/com/hourly/prod/uv.20160602/" rel="nofollow">link</a> from where I'm getting the file. The problem is I'm not able to understand the structure of the file so that I can get the data. I'm using <code>pygrib</code> to read the file.</p>
  
  <p>Here's the code I've tried:</p>
  
  <pre><code>grbs = pygrib.open('uv.t12z.grbf01.grib2')
  grb = grbs.select(name='UV index')[0]
  print grb.data(23.5,55.5)
  </code></pre>
  
  <p>What I'm trying to achieve is either iterate over all the lat longs and print the corresponding uvIndex value or enter a lat long and get the corresponding value. Read the docs of <code>pygrib</code> but couldn't find any suitable command that will serve my purpose. Please help.</p>