How to automatically set the extent based on information inside wrfout data.

[zemega]

Hello. I'm following the guide in this page. https://pratiman-91.github.io/2020/07/29/WRF-Surface-plot-using-Python.html. The code given is as below. The image output is as below.

import wrf
from netCDF4 import Dataset
import proplot as plot
import cartopy.crs as crs

# Download the dataset from https://www.unidata.ucar.edu/software/netcdf/examples/wrfout_v2_Lambert.nc
# Load the dataset
ncfile = Dataset('wrfout_v2_Lambert.nc')

# Get the variable
slp = wrf.getvar(ncfile, "slp")

# Get the latitude and longitude points
lats, lons = wrf.latlon_coords(slp)

# Get the cartopy mapping object
cart_proj = wrf.get_cartopy(slp)

#Plotting
fig, axs = plot.subplots(proj=cart_proj)

# Define extents
lat = [lats.min(), lats.max()]
lon = [lons.min(), lons.max()]

#format the plot
axs.format(
    lonlim=lon, latlim=lat,
    labels=True, innerborders=True
)

#Plot using contourf
m = axs.contourf(wrf.to_np(lons), wrf.to_np(lats), wrf.to_np(slp), 
                      transform=crs.PlateCarree(), cmap='roma_r')

#Adding colorbar with label
cbar = fig.colorbar(m, loc='b', label='Sea Level Pressure (hPa)') 

#Saving the figure
fig.savefig('slp.png')

As you can see, the data is really that rectangle, and there's a lot of empty space created. The best I can do is by referencing the XLONG and XLAT from the corners of the slp data, by using lonlim=[slp[0,-1].XLONG,slp[-1,0].XLONG],latlim=[slp[-1,0].XLAT,slp[0,-1].XLAT].

fig, axs = plot.subplots(proj=cart_proj)

# Define extents
lat = [lats.min(), lats.max()]
lon = [lons.min(), lons.max()]

#format the plot
axs.format(
    #lonlim=lon, latlim=lat,
    lonlim=[slp[0,-1].XLONG,slp[-1,0].XLONG],latlim=[slp[-1,0].XLAT,slp[0,-1].XLAT],
    labels=True, innerborders=True
)

#Plot using contourf
m = axs.contourf(wrf.to_np(lons), wrf.to_np(lats), wrf.to_np(slp), 
                      transform=crs.PlateCarree(), cmap='roma_r')

#Adding colorbar with label
cbar = fig.colorbar(m, loc='b', label='Sea Level Pressure (hPa)') 

#Saving the figure
fig.savefig('slp.png')

This leaves no empty space on the sides, but there's still empty spaces on top and bottom. I have tried other combination, but the others simply cutoff the data area.

I would like help with this. The wrf-python recommends cartopy, but the plots simply don't have any tick marks for latlon.

Edit 1:
This refers to the above code. How do I tell the codes above to use basemap instead of cartopy? I'm looking into plotting over the South Pole. And I do not have any success using Cartopy with the base matplotlib. I would like to try using proplot with basemap as the backend. I could not figure out where to insert backend = 'basemap'.