# [python #XTF-300986]: Follow-up on Pint Quantity problem

• Subject: [python #XTF-300986]: Follow-up on Pint Quantity problem
• Date: Fri, 04 Dec 2020 18:09:43 -0700

```Hi,

No problem. Thanks for sending it over. Working with this script
was...illuminating. Not because there's anything fundamentally wrong there, it
just helps to see how people tackle things, and more importantly be inspired to
see what challenges exist. And there were *many* challenges as I tweaked your
script to work like I wanted it to. So here's the version I arrived at:

import matplotlib as mpl
mpl.use('Agg')
import matplotlib.pyplot as plt
import numpy as np
from datetime import datetime
from siphon.catalog import TDSCatalog
import metpy.calc as mpcalc
from metpy.units import units
from metpy.plots import SkewT

# Use siphon to get a random weather model dataset
dt = datetime(2020, 7, 19, 0)
cat =
TDSCatalog(f"https://www.ncei.noaa.gov/thredds/catalog/model-rap130/{dt:%Y%m}/{dt:%Y%m%d}/catalog.xml";)
ds = cat.datasets[f"rap_130_{dt:%Y%m%d_%H%M_000.grb2}"]
data = ds.remote_access(use_xarray=True)
data = data.metpy.parse_cf()

# Get the data fields from the file
tmpk = data['Temperature_isobaric'][0,:,150,150] # Give it any random y,x

# Flip here and everything else will be consistent
tmpk = np.flip(tmpk)

# Pressure needs to go bottom to top--vertical always points to the
vertical coordinate
pres = tmpk.metpy.vertical

# Converts XArray to Pint-wrapping numpy using units metadata
# This *shouldn't* be needed but makes plotting work far more easily
tmpk = tmpk.metpy.unit_array
pres = pres.metpy.unit_array

# Initialize the plot and overlay the data
fig = plt.figure(figsize=(1600/96, 1600/96))
skew = SkewT(fig, rotation=45)
skew.plot(pres, tmpk, 'r', linewidth=3.) # This works fine

# Calculate a parcel profile
# Just use some dummy surface temps and dew points for the sake of this
example
tmpcsfc = 40. * units.degC
tdsfc = 20. * units.degC
parcel_prof = mpcalc.parcel_profile(pres, tmpcsfc, tdsfc)

# Set the plot to use degC
skew.ax.xaxis.set_units(units.degC)

Instead of using NCSS, I had it use OPeNDAP and xarray--which paves the way to
avoiding a lot of hand-manipulation of units. Unfortunately, the happy path is
not nearly as robust as I'd like.

If any of that is unclear, I'm happy to clarify. Thanks for some inspiration on
how we can make things better!

Ryan

> Here's the example script I was talking about on Twitter. Thanks again for
> all you do!

Ticket Details
===================
Ticket ID: XTF-300986
Department: Support Python
Priority: Low
Status: Closed
===================
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```