title: python load OpenDap to NetcdfFile
body: <p>I am opening netcdf data from an opendap server (a subset of the data) using an URL. When I open it the data is (as far as I can see) not actually loaded until the variable is requested. I would like to save the data to a file on disk, how would I do this?</p>
  
  <p>I currently have:</p>
  
  <pre><code>import numpy as np
  import netCDF4 as NC
  
  url = u'http://etc/etc/hourly?varname[0:1:10][0:1:30]'
  set = NC.Dataset(url) # I think data is not yet loaded here, only the "layout"
  varData = set.variables['varname'][:,:] # I think data is loaded here
  
  # now i want to save this data to a file (for example test.nc), set.close() obviously wont work
  </code></pre>
  
  <p>Hope someone can help, thanks!</p>