Help me beat my pythonist friend's code. Speeding up data reading with simple reduction from NetCDF file

[lmiq]

@aramirezreyes

But for this small example sometimes the first run takes 3 minutes and the other ones are much faster.

Compilation time should not depend on the size of the data (unless there is some specialized method that is called for large files), so it is possible to check that with a small set.