Warnings

[howff]

Some warnings that I am not sure how to solve:

1. global_scene = Scene
   No handlers could be found for logger "satpy.readers.yaml_reader"

2. global_scene.load([band_name]) - for overview of HRV meteosat
   /packages/pytroll/local/lib/python2.7/site-packages/satpy/readers/hrit_msg.py:1000: RuntimeWarning: divide by zero encountered in reciprocal
   data.data[:] **= -1

3. global_scene.save_dataset(band_name, 'my_nice_overview.png')
   /packages/pytroll/local/lib/python2.7/site-packages/trollimage/image.py:847: RuntimeWarning: invalid value encountered in power
   (1.0 / gamma),

[djhoese]

Thanks for the bug report. Note that all of these are just warnings which means they aren't errors and the code is likely working fine even when these are encountered. I appreciate you bringing these issues up though since it is always good for us to reduce future users' confusion.

1. This is due to some portions of the code using a python logger (via the builtin logging module). These could be fixed by running logging.basicConfig() by the user, but should probably be handled by satpy in some way (if possible).

2. This is due to there being masked values (NaNs) in the data being processed so any operation will warn that a NaN value was being used in calculations. The code being used should probably be doing inplace operations on the entire data array and taking advantage of masked arrays. However, since we are switching to xarray in the semi-near future this code will be rewritten anyway so we'll have to tackle it if it comes up again.

3. Same as 2 just in a different part of the code.

[djhoese]

The first warning has now been fixed in master by adding a NullHandler to the base 'satpy' logger. This warning also only showed up in Python 2.7 from what I can tell.

The other warnings still exist and will always exist unless extra (and in my opinion redundant) checks are done. I'll leave this open to make sure we mention somewhere in the documentation that warnings like this are expected where input data are invalid/NaN.

[djhoese]

I'm closing this as there isn't much we can do about NaN values causing warnings.