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[python #OTR-911008]: problem with Example MSLP and 1000-500 hPa Thickness with High and Low Symbols


Thanks for reaching out to us about this, and apologies for the delayed 
response. This error is occurring as NCEI has slightly changed their THREDDS 
Data Server access URLs. If you update your `ncss` URL from 
'../thredds/ncss/grid/narr-a-files/..' to 
'../thredds/ncss/model-narr-a-files/..' you will regain access. I will be going 
through our training material and updating these incorrect URLs. We will 
hopefully also look into making these errors more helpful for Siphon users.

However, your script will then run into a maskedarray+units issue resolved in 
our (more) up-to-date python-training page! We have archived this 
python-gallery and do not keep it up to date. We are currently exploring 
effective ways to communicate this to users who stumble across this older 
python-gallery. All you should need to do for your specific script to work is 
to change lines 99 and 100

  EMSL = data.variables['Pressure_reduced_to_MSL_msl'][:] * units.Pa


  EMSL = units.Quantity(data.variables['Pressure_reduced_to_MSL_msl'][:], 

and you should be good to go. Still, I strongly suggest checking out our 
currently maintained (though right now a little behind) python-training page at 
https://unidata.github.io/python-training/ with this specific example available 
as a notebook at 

I hope this helps, and feel free to reach out if there are any other issues. 

All the best,


> Hi all,
> I tried to setup the example to plot MSLP.
> I downloaded the example
> https://unidata.github.io/python-gallery/_downloads/191d328bde48c97aeb16e563101fee4d/HILO_Symbol_Plot.py
> ....but I struggle to load the data from NOAA with this error:
> /home/test/anaconda2/envs/pytroll/lib/python3.6/site-packages/distributed/config.py:20:
> YAMLLoadWarning: calling yaml.load() without Loader=... is deprecated,
> as the default Loader is unsafe. Please read https://msg.pyyaml.org/load
> for full details.
> defaults = yaml.load(f)
> Traceback (most recent call last):
> File "HILO_Symbol_Plot.py", line 77, in <module>
> 'narr-a_221_{0:%Y%m%d}_{0:%H}00_000.grb'.format(dattim))
> File
> "/home/test/anaconda2/envs/pytroll/lib/python3.6/site-packages/siphon/http_util.py",
> line 379, in __init__
> self._get_metadata()
> File
> "/home/test/anaconda2/envs/pytroll/lib/python3.6/site-packages/siphon/ncss.py",
> line 58, in _get_metadata
> root = ET.fromstring(meta_xml)
> File
> "/home/test/anaconda2/envs/pytroll/lib/python3.6/xml/etree/ElementTree.py",
> line 1315, in XML
> return parser.close()
> xml.etree.ElementTree.ParseError: no element found: line 1, column 0
> Any idea howto fix this?
> Thanks in advance!

Ticket Details
Ticket ID: OTR-911008
Department: Support Python
Priority: Low
Status: Closed
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