TypeError: 'GeometryCollection' object is not subscriptable (cartopy calling shapely)

[durack1]

Description

I have hit a repeatable, but confusing error with ~20 timesteps in a long ~1800 timestep global array. The error appears to be sensitive to the levels specified in the optional levels argument, and is reproduced below. It triggers a GeometryCollection error in the shapely library call (see traceback below).

I have included a working example below, which loops through two timesteps, the first works great plotting cleanly, and the second bombs, triggering the GeometryCollection bug. The error continues on subsequent timesteps, after ~20 or so, it starts to work again.

I would appreciate any pointers to resolving this issue, or tips at identifying a workaround to get me plotting through the problem ~20 timesteps.

Code to reproduce

# %% imports
import cartopy.crs as ccrs
import matplotlib.pyplot as plt
import numpy as np
from xarray import open_dataset

# %% load dataset
f = "cartopyLevelBugTwoTimesteps.nc"  # (file will be dropped below)
ds = open_dataset(f)
da = ds.siconc

# %% setup plot
levs1 = list(np.arange(-20, 121, 10))  # siconc
centralLon = 202

# %% step through working and failing timesteps
for time in np.arange(0, 2):
    print("Step:", time)
    ar = da.isel(time=time)
    fig = plt.figure(figsize=(10, 15))

    # Start subplots
    ax1 = fig.add_subplot(3, 1, 1,
                          projection=ccrs.Robinson(
                              central_longitude=centralLon,
                              globe=None,
                              false_easting=None,
                              false_northing=None,
                          ),
                          )
    cs1 = ax1.contourf(da.lon.data, da.lat.data, ar.data,
                       levs1,
                       transform=ccrs.PlateCarree(),
                       cmap="RdBu_r"
                       )
    plt.show()
    # time = 1; Should bomb with "TypeError: 'GeometryCollection' object is not subscriptable"

Data to reproduce

cartopyLevelBugTwoTimesteps.nc.gz

Traceback

Traceback (most recent call last):
  File ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132/lib/python3.10/site-packages/spyder_kernels/py3compat.py:356 in compat_exec
    exec(code, globals, locals)
  File ~/git/amipbcs/cartopyBug.py:41
    cs1 = ax1.contourf(da.lon.data, da.lat.data, ar.data,
  File ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132/lib/python3.10/site-packages/cartopy/mpl/geoaxes.py:318 in wrapper
    return func(self, *args, **kwargs)
  File ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132/lib/python3.10/site-packages/cartopy/mpl/geoaxes.py:362 in wrapper
    return func(self, *args, **kwargs)
  File ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132/lib/python3.10/site-packages/cartopy/mpl/geoaxes.py:1665 in contourf
    bboxes = [col.get_datalim(self.transData)
  File ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132/lib/python3.10/site-packages/cartopy/mpl/geoaxes.py:1665 in <listcomp>
    bboxes = [col.get_datalim(self.transData)
  File ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132/lib/python3.10/site-packages/matplotlib/collections.py:266 in get_datalim
    paths = [transform.transform_path_non_affine(p) for p in paths]
  File ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132/lib/python3.10/site-packages/matplotlib/collections.py:266 in <listcomp>
    paths = [transform.transform_path_non_affine(p) for p in paths]
  File ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132/lib/python3.10/site-packages/matplotlib/transforms.py:2431 in transform_path_non_affine
    return self._a.transform_path_non_affine(path)
  File ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132/lib/python3.10/site-packages/cartopy/mpl/geoaxes.py:190 in transform_path_non_affine
    proj_geom = self.target_projection.project_geometry(
  File ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132/lib/python3.10/site-packages/cartopy/crs.py:808 in project_geometry
    return getattr(self, method_name)(geometry, src_crs)
  File ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132/lib/python3.10/site-packages/cartopy/crs.py:963 in _project_polygon
    return self._rings_to_multi_polygon(rings, is_ccw)
  File ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132/lib/python3.10/site-packages/cartopy/crs.py:1224 in _rings_to_multi_polygon
    multi_poly = sgeom.MultiPolygon(polygon_bits)
  File ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132/lib/python3.10/site-packages/shapely/geometry/multipolygon.py:79 in __new__
    shell = ob[0]
TypeError: 'GeometryCollection' object is not subscriptable

Full environment definition

Operating system

RHEL7.9
(xcd050xes071spy543mat371car0211ipy8132) bash-4.2$ uname -a
Linux detect 3.10.0-1160.76.1.el7.x86_64 #1 SMP Tue Jul 26 14:15:37 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

Cartopy version

cartopy.__version__**
'0.21.1'

conda list

(xcd050xes071spy543mat371car0211ipy8132) bash-4.2$ conda list
# packages in environment at ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132:
#
# Name                    Version                   Build  Channel
_libgcc_mutex             0.1                 conda_forge    conda-forge
_openmp_mutex             4.5                       2_gnu    conda-forge
alabaster                 0.7.13             pyhd8ed1ab_0    conda-forge
alsa-lib                  1.2.8                h166bdaf_0    conda-forge
anyio                     3.6.2              pyhd8ed1ab_0    conda-forge
argon2-cffi               21.3.0             pyhd8ed1ab_0    conda-forge
argon2-cffi-bindings      21.2.0          py310h5764c6d_3    conda-forge
arrow                     1.2.3              pyhd8ed1ab_0    conda-forge
arrow-cpp                 11.0.0          ha770c72_16_cpu    conda-forge
astroid                   2.15.4          py310hff52083_0    conda-forge
asttokens                 2.2.1              pyhd8ed1ab_0    conda-forge
atomicwrites              1.4.1              pyhd8ed1ab_0    conda-forge
attr                      2.5.1                h166bdaf_1    conda-forge
attrs                     23.1.0             pyh71513ae_1    conda-forge
autopep8                  2.0.2              pyhd8ed1ab_0    conda-forge
aws-c-auth                0.6.26               h2c7c9e7_6    conda-forge
aws-c-cal                 0.5.26               h71eb795_0    conda-forge
aws-c-common              0.8.17               hd590300_0    conda-forge
aws-c-compression         0.2.16               h4f47f36_6    conda-forge
aws-c-event-stream        0.2.20               h69ce273_6    conda-forge
aws-c-http                0.7.7                h7b8353a_3    conda-forge
aws-c-io                  0.13.21              hcccde9c_3    conda-forge
aws-c-mqtt                0.8.6               h3a1964a_15    conda-forge
aws-c-s3                  0.2.8                h0933b68_4    conda-forge
aws-c-sdkutils            0.1.9                h4f47f36_1    conda-forge
aws-checksums             0.1.14               h4f47f36_6    conda-forge
aws-crt-cpp               0.19.9               h85076f6_5    conda-forge
aws-sdk-cpp               1.10.57             hf40e4db_10    conda-forge
babel                     2.12.1             pyhd8ed1ab_1    conda-forge
backcall                  0.2.0              pyh9f0ad1d_0    conda-forge
backports                 1.0                pyhd8ed1ab_3    conda-forge
backports.functools_lru_cache 1.6.4              pyhd8ed1ab_0    conda-forge
beautifulsoup4            4.12.2             pyha770c72_0    conda-forge
binaryornot               0.4.4                      py_1    conda-forge
black                     23.3.0          py310hff52083_1    conda-forge
bleach                    6.0.0              pyhd8ed1ab_0    conda-forge
blosc                     1.21.3               hafa529b_0    conda-forge
bokeh                     3.1.0              pyhd8ed1ab_0    conda-forge
bottleneck                1.3.7           py310h0a54255_0    conda-forge
brotli                    1.0.9                h166bdaf_8    conda-forge
brotli-bin                1.0.9                h166bdaf_8    conda-forge
brotlipy                  0.7.0           py310h5764c6d_1005    conda-forge
bzip2                     1.0.8                h7f98852_4    conda-forge
c-ares                    1.18.1               h7f98852_0    conda-forge
ca-certificates           2023.5.7             hbcca054_0    conda-forge
cairo                     1.16.0            h35add3b_1015    conda-forge
cartopy                   0.21.1          py310h7eb24ba_1    conda-forge
certifi                   2023.5.7           pyhd8ed1ab_0    conda-forge
cf_xarray                 0.8.0              pyhd8ed1ab_0    conda-forge
cffi                      1.15.1          py310h255011f_3    conda-forge
cftime                    1.6.2           py310hde88566_1    conda-forge
chardet                   5.1.0           py310hff52083_0    conda-forge
charset-normalizer        3.1.0              pyhd8ed1ab_0    conda-forge
click                     8.1.3           unix_pyhd8ed1ab_2    conda-forge
cloudpickle               2.2.1              pyhd8ed1ab_0    conda-forge
colorama                  0.4.6              pyhd8ed1ab_0    conda-forge
comm                      0.1.3              pyhd8ed1ab_0    conda-forge
contourpy                 1.0.7           py310hdf3cbec_0    conda-forge
cookiecutter              2.1.1              pyh6c4a22f_0    conda-forge
cryptography              40.0.2          py310h34c0648_0    conda-forge
curl                      8.0.1                h588be90_0    conda-forge
cycler                    0.11.0             pyhd8ed1ab_0    conda-forge
cytoolz                   0.12.0          py310h5764c6d_1    conda-forge
dask                      2023.4.1           pyhd8ed1ab_0    conda-forge
dask-core                 2023.4.1           pyhd8ed1ab_0    conda-forge
dbus                      1.13.6               h5008d03_3    conda-forge
debugpy                   1.6.7           py310heca2aa9_0    conda-forge
decorator                 5.1.1              pyhd8ed1ab_0    conda-forge
defusedxml                0.7.1              pyhd8ed1ab_0    conda-forge
diff-match-patch          20200713           pyh9f0ad1d_0    conda-forge
dill                      0.3.6              pyhd8ed1ab_1    conda-forge
distributed               2023.4.1           pyhd8ed1ab_0    conda-forge
docstring-to-markdown     0.12               pyhd8ed1ab_0    conda-forge
docutils                  0.19            py310hff52083_1    conda-forge
entrypoints               0.4                pyhd8ed1ab_0    conda-forge
esmf                      8.4.2           mpi_mpich_h742b71d_100    conda-forge
esmpy                     8.4.2              pyhc1e730c_0    conda-forge
executing                 1.2.0              pyhd8ed1ab_0    conda-forge
expat                     2.5.0                hcb278e6_1    conda-forge
fftw                      3.3.10          nompi_hc118613_107    conda-forge
flake8                    6.0.0              pyhd8ed1ab_0    conda-forge
flit-core                 3.8.0              pyhd8ed1ab_0    conda-forge
font-ttf-dejavu-sans-mono 2.37                 hab24e00_0    conda-forge
font-ttf-inconsolata      3.000                h77eed37_0    conda-forge
font-ttf-source-code-pro  2.038                h77eed37_0    conda-forge
font-ttf-ubuntu           0.83                 hab24e00_0    conda-forge
fontconfig                2.14.2               h14ed4e7_0    conda-forge
fonts-conda-ecosystem     1                             0    conda-forge
fonts-conda-forge         1                             0    conda-forge
fonttools                 4.39.3          py310h1fa729e_0    conda-forge
freetype                  2.12.1               hca18f0e_1    conda-forge
fsspec                    2023.5.0           pyh1a96a4e_0    conda-forge
geos                      3.11.2               hcb278e6_0    conda-forge
gettext                   0.21.1               h27087fc_0    conda-forge
gflags                    2.2.2             he1b5a44_1004    conda-forge
giflib                    5.2.1                h0b41bf4_3    conda-forge
glib                      2.76.2               hfc55251_0    conda-forge
glib-tools                2.76.2               hfc55251_0    conda-forge
glog                      0.6.0                h6f12383_0    conda-forge
graphite2                 1.3.13            h58526e2_1001    conda-forge
gst-plugins-base          1.22.0               h4243ec0_2    conda-forge
gstreamer                 1.22.0               h25f0c4b_2    conda-forge
gstreamer-orc             0.4.33               h166bdaf_0    conda-forge
harfbuzz                  6.0.0                h3ff4399_1    conda-forge
hdf4                      4.2.15               h501b40f_6    conda-forge
hdf5                      1.14.0          mpi_mpich_hcccbd3f_3    conda-forge
icu                       72.1                 hcb278e6_0    conda-forge
idna                      3.4                pyhd8ed1ab_0    conda-forge
imagesize                 1.4.1              pyhd8ed1ab_0    conda-forge
importlib-metadata        6.6.0              pyha770c72_0    conda-forge
importlib_metadata        6.6.0                hd8ed1ab_0    conda-forge
importlib_resources       5.12.0             pyhd8ed1ab_0    conda-forge
inflection                0.5.1              pyh9f0ad1d_0    conda-forge
intervaltree              3.1.0              pyhd8ed1ab_1    conda-forge
ipykernel                 6.23.0             pyh210e3f2_0    conda-forge
ipython                   8.13.2             pyh41d4057_0    conda-forge
ipython_genutils          0.2.0                      py_1    conda-forge
ipywidgets                8.0.6              pyhd8ed1ab_0    conda-forge
isort                     5.12.0             pyhd8ed1ab_1    conda-forge
jack                      1.9.22               h11f4161_0    conda-forge
jaraco.classes            3.2.3              pyhd8ed1ab_0    conda-forge
jedi                      0.18.2             pyhd8ed1ab_0    conda-forge
jeepney                   0.8.0              pyhd8ed1ab_0    conda-forge
jellyfish                 0.9.0           py310h5764c6d_2    conda-forge
jinja2                    3.1.2              pyhd8ed1ab_1    conda-forge
jinja2-time               0.2.0              pyhd8ed1ab_3    conda-forge
jsonschema                4.17.3             pyhd8ed1ab_0    conda-forge
jupyter                   1.0.0           py310hff52083_8    conda-forge
jupyter_client            8.2.0              pyhd8ed1ab_0    conda-forge
jupyter_console           6.6.3              pyhd8ed1ab_0    conda-forge
jupyter_core              5.3.0           py310hff52083_0    conda-forge
jupyter_events            0.6.3              pyhd8ed1ab_0    conda-forge
jupyter_server            2.5.0              pyhd8ed1ab_0    conda-forge
jupyter_server_terminals  0.4.4              pyhd8ed1ab_1    conda-forge
jupyterlab_pygments       0.2.2              pyhd8ed1ab_0    conda-forge
jupyterlab_widgets        3.0.7              pyhd8ed1ab_0    conda-forge
keyring                   23.13.1         py310hff52083_0    conda-forge
keyutils                  1.6.1                h166bdaf_0    conda-forge
kiwisolver                1.4.4           py310hbf28c38_1    conda-forge
krb5                      1.20.1               h81ceb04_0    conda-forge
lame                      3.100             h166bdaf_1003    conda-forge
lazy-object-proxy         1.9.0           py310h1fa729e_0    conda-forge
lcms2                     2.15                 haa2dc70_1    conda-forge
ld_impl_linux-64          2.40                 h41732ed_0    conda-forge
lerc                      4.0.0                h27087fc_0    conda-forge
libabseil                 20230125.0      cxx17_hcb278e6_1    conda-forge
libaec                    1.0.6                hcb278e6_1    conda-forge
libarrow                  11.0.0          h8dc56a0_16_cpu    conda-forge
libblas                   3.9.0           16_linux64_openblas    conda-forge
libbrotlicommon           1.0.9                h166bdaf_8    conda-forge
libbrotlidec              1.0.9                h166bdaf_8    conda-forge
libbrotlienc              1.0.9                h166bdaf_8    conda-forge
libcap                    2.67                 he9d0100_0    conda-forge
libcblas                  3.9.0           16_linux64_openblas    conda-forge
libclang                  16.0.3          default_h83cc7fd_0    conda-forge
libclang13                16.0.3          default_hd781213_0    conda-forge
libcrc32c                 1.1.2                h9c3ff4c_0    conda-forge
libcups                   2.3.3                h36d4200_3    conda-forge
libcurl                   8.0.1                h588be90_0    conda-forge
libdb                     6.2.32               h9c3ff4c_0    conda-forge
libdeflate                1.18                 h0b41bf4_0    conda-forge
libedit                   3.1.20191231         he28a2e2_2    conda-forge
libev                     4.33                 h516909a_1    conda-forge
libevent                  2.1.10               h28343ad_4    conda-forge
libexpat                  2.5.0                hcb278e6_1    conda-forge
libffi                    3.4.2                h7f98852_5    conda-forge
libflac                   1.4.2                h27087fc_0    conda-forge
libgcc-ng                 12.2.0              h65d4601_19    conda-forge
libgcrypt                 1.10.1               h166bdaf_0    conda-forge
libgfortran-ng            12.2.0              h69a702a_19    conda-forge
libgfortran5              12.2.0              h337968e_19    conda-forge
libglib                   2.76.2               hebfc3b9_0    conda-forge
libgomp                   12.2.0              h65d4601_19    conda-forge
libgoogle-cloud           2.8.0                hac9eb74_2    conda-forge
libgpg-error              1.46                 h620e276_0    conda-forge
libgrpc                   1.54.1               hcf146ea_0    conda-forge
libiconv                  1.17                 h166bdaf_0    conda-forge
libjpeg-turbo             2.1.5.1              h0b41bf4_0    conda-forge
liblapack                 3.9.0           16_linux64_openblas    conda-forge
libllvm11                 11.1.0               he0ac6c6_5    conda-forge
libllvm16                 16.0.3               hbf9e925_1    conda-forge
libnetcdf                 4.9.2           mpi_mpich_h53eaf7b_4    conda-forge
libnghttp2                1.52.0               h61bc06f_0    conda-forge
libnsl                    2.0.0                h7f98852_0    conda-forge
libnuma                   2.0.16               h0b41bf4_1    conda-forge
libogg                    1.3.4                h7f98852_1    conda-forge
libopenblas               0.3.21          pthreads_h78a6416_3    conda-forge
libopus                   1.3.1                h7f98852_1    conda-forge
libpng                    1.6.39               h753d276_0    conda-forge
libpq                     15.2                 hb675445_0    conda-forge
libprotobuf               3.21.12              h3eb15da_0    conda-forge
libsndfile                1.2.0                hb75c966_0    conda-forge
libsodium                 1.0.18               h36c2ea0_1    conda-forge
libspatialindex           1.9.3                h9c3ff4c_4    conda-forge
libsqlite                 3.40.0               h753d276_1    conda-forge
libssh2                   1.10.0               hf14f497_3    conda-forge
libstdcxx-ng              12.2.0              h46fd767_19    conda-forge
libsystemd0               253                  h8c4010b_1    conda-forge
libthrift                 0.18.1               h5e4af38_0    conda-forge
libtiff                   4.5.0                ha587672_6    conda-forge
libtool                   2.4.7                h27087fc_0    conda-forge
libudev1                  253                  h0b41bf4_1    conda-forge
libutf8proc               2.8.0                h166bdaf_0    conda-forge
libuuid                   2.38.1               h0b41bf4_0    conda-forge
libvorbis                 1.3.7                h9c3ff4c_0    conda-forge
libwebp                   1.3.0                hb47c5f0_0    conda-forge
libwebp-base              1.3.0                h0b41bf4_0    conda-forge
libxcb                    1.13              h7f98852_1004    conda-forge
libxkbcommon              1.5.0                h79f4944_1    conda-forge
libxml2                   2.10.4               hfdac1af_0    conda-forge
libxslt                   1.1.37               h873f0b0_0    conda-forge
libzip                    1.9.2                hc929e4a_1    conda-forge
libzlib                   1.2.13               h166bdaf_4    conda-forge
llvmlite                  0.39.1          py310h58363a5_1    conda-forge
locket                    1.0.0              pyhd8ed1ab_0    conda-forge
lxml                      4.9.2           py310hbdc0903_0    conda-forge
lz4                       4.3.2           py310h0cfdcf0_0    conda-forge
lz4-c                     1.9.4                hcb278e6_0    conda-forge
markupsafe                2.1.2           py310h1fa729e_0    conda-forge
matplotlib                3.7.1           py310hff52083_0    conda-forge
matplotlib-base           3.7.1           py310he60537e_0    conda-forge
matplotlib-inline         0.1.6              pyhd8ed1ab_0    conda-forge
mccabe                    0.7.0              pyhd8ed1ab_0    conda-forge
mistune                   2.0.5              pyhd8ed1ab_0    conda-forge
more-itertools            9.1.0              pyhd8ed1ab_0    conda-forge
mpg123                    1.31.3               hcb278e6_0    conda-forge
mpi                       1.0                       mpich    conda-forge
mpich                     4.1.1              h846660c_100    conda-forge
msgpack-python            1.0.5           py310hdf3cbec_0    conda-forge
munkres                   1.1.4              pyh9f0ad1d_0    conda-forge
mypy_extensions           1.0.0              pyha770c72_0    conda-forge
mysql-common              8.0.32               hf1915f5_2    conda-forge
mysql-libs                8.0.32               hca2cd23_2    conda-forge
nbclassic                 1.0.0              pyhb4ecaf3_1    conda-forge
nbclient                  0.7.4              pyhd8ed1ab_0    conda-forge
nbconvert                 7.3.1              pyhd8ed1ab_0    conda-forge
nbconvert-core            7.3.1              pyhd8ed1ab_0    conda-forge
nbconvert-pandoc          7.3.1              pyhd8ed1ab_0    conda-forge
nbformat                  5.8.0              pyhd8ed1ab_0    conda-forge
ncurses                   6.3                  h27087fc_1    conda-forge
nest-asyncio              1.5.6              pyhd8ed1ab_0    conda-forge
netcdf-fortran            4.6.0           mpi_mpich_hebcc635_5    conda-forge
netcdf4                   1.6.3           nompi_py310h2d0b64f_102    conda-forge
notebook                  6.5.4              pyha770c72_0    conda-forge
notebook-shim             0.2.3              pyhd8ed1ab_0    conda-forge
nspr                      4.35                 h27087fc_0    conda-forge
nss                       3.89                 he45b914_0    conda-forge
numba                     0.56.4          py310h0e39c9b_1    conda-forge
numpy                     1.23.5          py310h53a5b5f_0    conda-forge
numpydoc                  1.5.0              pyhd8ed1ab_0    conda-forge
openjpeg                  2.5.0                hfec8fc6_2    conda-forge
openssl                   3.1.0                hd590300_3    conda-forge
orc                       1.8.3                hfdbbad2_0    conda-forge
packaging                 23.1               pyhd8ed1ab_0    conda-forge
pandas                    2.0.1           py310h7cbd5c2_1    conda-forge
pandoc                    2.19.2               h32600fe_2    conda-forge
pandocfilters             1.5.0              pyhd8ed1ab_0    conda-forge
parallelio                2.5.10          mpi_mpich_h0b4b548_102    conda-forge
parquet-cpp               1.5.1                         2    conda-forge
parso                     0.8.3              pyhd8ed1ab_0    conda-forge
partd                     1.4.0              pyhd8ed1ab_0    conda-forge
pathspec                  0.11.1             pyhd8ed1ab_0    conda-forge
pcre2                     10.40                hc3806b6_0    conda-forge
pexpect                   4.8.0              pyh1a96a4e_2    conda-forge
pickleshare               0.7.5                   py_1003    conda-forge
pillow                    9.5.0           py310h065c6d2_0    conda-forge
pip                       23.1.2             pyhd8ed1ab_0    conda-forge
pixman                    0.40.0               h36c2ea0_0    conda-forge
pkgutil-resolve-name      1.3.10             pyhd8ed1ab_0    conda-forge
platformdirs              3.5.0              pyhd8ed1ab_0    conda-forge
pluggy                    1.0.0              pyhd8ed1ab_5    conda-forge
ply                       3.11                       py_1    conda-forge
pooch                     1.7.0              pyha770c72_3    conda-forge
proj                      9.2.0                h8ffa02c_0    conda-forge
prometheus_client         0.16.0             pyhd8ed1ab_0    conda-forge
prompt-toolkit            3.0.38             pyha770c72_0    conda-forge
prompt_toolkit            3.0.38               hd8ed1ab_0    conda-forge
psutil                    5.9.5           py310h1fa729e_0    conda-forge
pthread-stubs             0.4               h36c2ea0_1001    conda-forge
ptyprocess                0.7.0              pyhd3deb0d_0    conda-forge
pulseaudio                16.1                 hcb278e6_3    conda-forge
pulseaudio-client         16.1                 h5195f5e_3    conda-forge
pulseaudio-daemon         16.1                 ha8d29e2_3    conda-forge
pure_eval                 0.2.2              pyhd8ed1ab_0    conda-forge
pyarrow                   11.0.0          py310he6bfd7f_16_cpu    conda-forge
pycodestyle               2.10.0             pyhd8ed1ab_0    conda-forge
pycparser                 2.21               pyhd8ed1ab_0    conda-forge
pydocstyle                6.3.0              pyhd8ed1ab_0    conda-forge
pyflakes                  3.0.1              pyhd8ed1ab_0    conda-forge
pygments                  2.15.1             pyhd8ed1ab_0    conda-forge
pylint                    2.17.4             pyhd8ed1ab_0    conda-forge
pylint-venv               3.0.1              pyhd8ed1ab_0    conda-forge
pyls-spyder               0.4.0              pyhd8ed1ab_0    conda-forge
pyopenssl                 23.1.1             pyhd8ed1ab_0    conda-forge
pyparsing                 3.0.9              pyhd8ed1ab_0    conda-forge
pyproj                    3.5.0           py310hb814896_1    conda-forge
pyqt                      5.15.7          py310hab646b1_3    conda-forge
pyqt5-sip                 12.11.0         py310heca2aa9_3    conda-forge
pyqtwebengine             5.15.7          py310h1165ae2_3    conda-forge
pyrsistent                0.19.3          py310h1fa729e_0    conda-forge
pyshp                     2.3.1              pyhd8ed1ab_0    conda-forge
pysocks                   1.7.1              pyha2e5f31_6    conda-forge
python                    3.10.10         he550d4f_0_cpython    conda-forge
python-dateutil           2.8.2              pyhd8ed1ab_0    conda-forge
python-fastjsonschema     2.16.3             pyhd8ed1ab_0    conda-forge
python-json-logger        2.0.7              pyhd8ed1ab_0    conda-forge
python-lsp-black          1.2.1              pyhd8ed1ab_0    conda-forge
python-lsp-jsonrpc        1.0.0              pyhd8ed1ab_0    conda-forge
python-lsp-server         1.7.2              pyhd8ed1ab_0    conda-forge
python-lsp-server-base    1.7.2              pyhd8ed1ab_0    conda-forge
python-slugify            8.0.1              pyhd8ed1ab_1    conda-forge
python-tzdata             2023.3             pyhd8ed1ab_0    conda-forge
python_abi                3.10                    3_cp310    conda-forge
pytoolconfig              1.2.5              pyhd8ed1ab_0    conda-forge
pytz                      2023.3             pyhd8ed1ab_0    conda-forge
pyxdg                     0.28               pyhd8ed1ab_0    conda-forge
pyyaml                    6.0             py310h5764c6d_5    conda-forge
pyzmq                     25.0.2          py310h059b190_0    conda-forge
qdarkstyle                3.1                pyhd8ed1ab_0    conda-forge
qstylizer                 0.2.2              pyhd8ed1ab_0    conda-forge
qt-main                   5.15.8              h5c52f38_10    conda-forge
qt-webengine              5.15.8               h77d6d84_0    conda-forge
qtawesome                 1.2.3              pyhd8ed1ab_0    conda-forge
qtconsole                 5.4.3              pyhd8ed1ab_0    conda-forge
qtconsole-base            5.4.3              pyha770c72_0    conda-forge
qtpy                      2.3.1              pyhd8ed1ab_0    conda-forge
re2                       2023.02.02           hcb278e6_0    conda-forge
readline                  8.2                  h8228510_1    conda-forge
requests                  2.29.0             pyhd8ed1ab_0    conda-forge
rfc3339-validator         0.1.4              pyhd8ed1ab_0    conda-forge
rfc3986-validator         0.1.1              pyh9f0ad1d_0    conda-forge
rope                      1.8.0              pyhd8ed1ab_0    conda-forge
rtree                     1.0.1           py310hbdcdc62_1    conda-forge
s2n                       1.3.42               h3358134_0    conda-forge
scipy                     1.10.1          py310h8deb116_1    conda-forge
secretstorage             3.3.3           py310hff52083_1    conda-forge
send2trash                1.8.2              pyh41d4057_0    conda-forge
setuptools                67.7.2             pyhd8ed1ab_0    conda-forge
shapely                   2.0.1           py310h056c13c_1    conda-forge
sip                       6.7.9           py310hc6cd4ac_0    conda-forge
six                       1.16.0             pyh6c4a22f_0    conda-forge
snappy                    1.1.10               h9fff704_0    conda-forge
sniffio                   1.3.0              pyhd8ed1ab_0    conda-forge
snowballstemmer           2.2.0              pyhd8ed1ab_0    conda-forge
sortedcontainers          2.4.0              pyhd8ed1ab_0    conda-forge
soupsieve                 2.3.2.post1        pyhd8ed1ab_0    conda-forge
sparse                    0.14.0             pyhd8ed1ab_0    conda-forge
sphinx                    7.0.0              pyhd8ed1ab_0    conda-forge
sphinxcontrib-applehelp   1.0.4              pyhd8ed1ab_0    conda-forge
sphinxcontrib-devhelp     1.0.2                      py_0    conda-forge
sphinxcontrib-htmlhelp    2.0.1              pyhd8ed1ab_0    conda-forge
sphinxcontrib-jsmath      1.0.1                      py_0    conda-forge
sphinxcontrib-qthelp      1.0.3                      py_0    conda-forge
sphinxcontrib-serializinghtml 1.1.5              pyhd8ed1ab_2    conda-forge
spyder                    5.4.3           py310hff52083_0    conda-forge
spyder-kernels            2.4.3           unix_pyhd8ed1ab_0    conda-forge
sqlite                    3.40.0               h4ff8645_1    conda-forge
stack_data                0.6.2              pyhd8ed1ab_0    conda-forge
tblib                     1.7.0              pyhd8ed1ab_0    conda-forge
terminado                 0.17.1             pyh41d4057_0    conda-forge
text-unidecode            1.3                        py_0    conda-forge
textdistance              4.5.0              pyhd8ed1ab_0    conda-forge
three-merge               0.1.1              pyh9f0ad1d_0    conda-forge
tinycss2                  1.2.1              pyhd8ed1ab_0    conda-forge
tk                        8.6.12               h27826a3_0    conda-forge
toml                      0.10.2             pyhd8ed1ab_0    conda-forge
tomli                     2.0.1              pyhd8ed1ab_0    conda-forge
tomlkit                   0.11.8             pyha770c72_0    conda-forge
toolz                     0.12.0             pyhd8ed1ab_0    conda-forge
tornado                   6.3             py310h1fa729e_0    conda-forge
traitlets                 5.9.0              pyhd8ed1ab_0    conda-forge
typing-extensions         4.5.0                hd8ed1ab_0    conda-forge
typing_extensions         4.5.0              pyha770c72_0    conda-forge
tzdata                    2023c                h71feb2d_0    conda-forge
ucx                       1.14.0               h3484d09_2    conda-forge
ujson                     5.7.0           py310heca2aa9_0    conda-forge
unicodedata2              15.0.0          py310h5764c6d_0    conda-forge
unidecode                 1.3.6              pyhd8ed1ab_0    conda-forge
urllib3                   1.26.15            pyhd8ed1ab_0    conda-forge
watchdog                  3.0.0           py310hff52083_0    conda-forge
wcwidth                   0.2.6              pyhd8ed1ab_0    conda-forge
webencodings              0.5.1                      py_1    conda-forge
websocket-client          1.5.1              pyhd8ed1ab_0    conda-forge
whatthepatch              1.0.5              pyhd8ed1ab_0    conda-forge
wheel                     0.40.0             pyhd8ed1ab_0    conda-forge
widgetsnbextension        4.0.7              pyhd8ed1ab_0    conda-forge
wrapt                     1.15.0          py310h1fa729e_0    conda-forge
wurlitzer                 3.0.3              pyhd8ed1ab_0    conda-forge
xarray                    2023.4.2           pyhd8ed1ab_0    conda-forge
xcb-util                  0.4.0                h516909a_0    conda-forge
xcb-util-image            0.4.0                h166bdaf_0    conda-forge
xcb-util-keysyms          0.4.0                h516909a_0    conda-forge
xcb-util-renderutil       0.3.9                h166bdaf_0    conda-forge
xcb-util-wm               0.4.1                h516909a_0    conda-forge
xcdat                     0.5.0              pyhd8ed1ab_0    conda-forge
xesmf                     0.7.1              pyhd8ed1ab_0    conda-forge
xkeyboard-config          2.38                 h0b41bf4_0    conda-forge
xorg-kbproto              1.0.7             h7f98852_1002    conda-forge
xorg-libice               1.0.10               h7f98852_0    conda-forge
xorg-libsm                1.2.3             hd9c2040_1000    conda-forge
xorg-libx11               1.8.4                h0b41bf4_0    conda-forge
xorg-libxau               1.0.9                h7f98852_0    conda-forge
xorg-libxdmcp             1.1.3                h7f98852_0    conda-forge
xorg-libxext              1.3.4                h0b41bf4_2    conda-forge
xorg-libxrender           0.9.10            h7f98852_1003    conda-forge
xorg-renderproto          0.11.1            h7f98852_1002    conda-forge
xorg-xextproto            7.3.0             h0b41bf4_1003    conda-forge
xorg-xf86vidmodeproto     2.3.1             h7f98852_1002    conda-forge
xorg-xproto               7.0.31            h7f98852_1007    conda-forge
xyzservices               2023.2.0           pyhd8ed1ab_0    conda-forge
xz                        5.2.6                h166bdaf_0    conda-forge
yaml                      0.2.5                h7f98852_2    conda-forge
yapf                      0.32.0             pyhd8ed1ab_0    conda-forge
zeromq                    4.3.4                h9c3ff4c_1    conda-forge
zict                      3.0.0              pyhd8ed1ab_0    conda-forge
zipp                      3.15.0             pyhd8ed1ab_0    conda-forge
zlib                      1.2.13               h166bdaf_4    conda-forge
zstd                      1.5.2                h3eb15da_6    conda-forge

pip list

nil

[greglucas]

This is likely some bad projection going on when transforming the geometries near a boundary. As a workaround, you can use the transform_first keyword which should avoid that path. https://scitools.org.uk/cartopy/docs/latest/gallery/scalar_data/contour_transforms.html#sphx-glr-gallery-scalar-data-contour-transforms-py

[durack1]

Thanks @greglucas! This tweak gets me back up and running again, great.

Should I close this issue, or leave this open for a more permanent diagnosis and fix? Apologies, I became confused as to what was going on, so without guidance you will not be getting a PR from me.

[greglucas]

I think we should leave it open and hope for a better solution rather than a workaround.

If you're interested in tackling this that would be great! It may not be too difficult, but it is sometimes hard to tell how deep into the code you'll have to get. If you want some guidance, I'd suggest isolating the failure geometry from the contour call. Adding some print or to_wkt() statements into the geometry transform region of the code should help get the one right before the failure.

  File ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132/lib/python3.10/site-packages/cartopy/crs.py:963 in _project_polygon
    return self._rings_to_multi_polygon(rings, is_ccw)
  File ~/mambaforge/envs/xcd050xes071spy543mat371car0211ipy8132/lib/python3.10/site-packages/cartopy/crs.py:1224 in _rings_to_multi_polygon
    multi_poly = sgeom.MultiPolygon(polygon_bits)

Then find out why that input geometry gets transformed into an output GeometryCollection and what geometries are in that GeometryCollection, maybe it is as simple as removing any extraneous point geometries after cutting/stitching.

[david-shu]

I encountered the same problem. Trace to cartopy.crs.Projection_ Rings_ To_ Multi_ Polygon method. When boundary_poly. intersection (polygon), a GeoCollection object is obtained instead of a Polygon object, resulting in Exception thrown when sgeom.MultiPolygon(polygon_bits).

from shapely.geometry.collection import GeometryCollection
import shapely.geometry as sgeom
from shapely.prepared import prep

def _rings_to_multi_polygon(self, rings, is_ccw):
    exterior_rings = []
    interior_rings = []
    for ring in rings:
        if ring.is_ccw != is_ccw:
            interior_rings.append(ring)
        else:
            exterior_rings.append(ring)

    polygon_bits = []

    # Turn all the exterior rings into polygon definitions,
    # "slurping up" any interior rings they contain.
    for exterior_ring in exterior_rings:
        polygon = sgeom.Polygon(exterior_ring)
        prep_polygon = prep(polygon)
        holes = []
        for interior_ring in interior_rings[:]:
            if prep_polygon.contains(interior_ring):
                holes.append(interior_ring)
                interior_rings.remove(interior_ring)
            elif polygon.crosses(interior_ring):
                # Likely that we have an invalid geometry such as
                # that from #509 or #537.
                holes.append(interior_ring)
                interior_rings.remove(interior_ring)
        polygon_bits.append((exterior_ring.coords,
                             [ring.coords for ring in holes]))

    # Any left over "interior" rings need "inverting" with respect
    # to the boundary.
    if interior_rings:
        boundary_poly = self.domain
        x3, y3, x4, y4 = boundary_poly.bounds
        bx = (x4 - x3) * 0.1
        by = (y4 - y3) * 0.1
        x3 -= bx
        y3 -= by
        x4 += bx
        y4 += by
        for ring in interior_rings:
            # Use shapely buffer in an attempt to fix invalid geometries
            polygon = sgeom.Polygon(ring).buffer(0)
            if not polygon.is_empty and polygon.is_valid:
                x1, y1, x2, y2 = polygon.bounds
                bx = (x2 - x1) * 0.1
                by = (y2 - y1) * 0.1
                x1 -= bx
                y1 -= by
                x2 += bx
                y2 += by
                box = sgeom.box(min(x1, x3), min(y1, y3),
                                max(x2, x4), max(y2, y4))

                # Invert the polygon
                polygon = box.difference(polygon)
                
                # Intersect the inverted polygon with the boundary
                polygon = boundary_poly.intersection(polygon)
                if not polygon.is_empty:
                    polygon_bits.append(polygon)
                    
    if polygon_bits:
        ##### added by david.shu ###################################
        polygon_bits2 = []
        for polygon in polygon_bits:
            if isinstance( polygon, GeometryCollection ):
                for g in polygon.geoms:
                    if isinstance( g, sgeom.Polygon ):
                        polygon_bits2.append( g )
                    else:
                        print( f'{type(g)} found. but Polygon required.' )
            else:
                polygon_bits2.append( polygon )
        polygon_bits = polygon_bits2 
        #######################################################
        
        multi_poly = sgeom.MultiPolygon(polygon_bits)
    else:
        multi_poly = sgeom.MultiPolygon()
    return multi_poly        

ccrs.Projection._rings_to_multi_polygon = _rings_to_multi_polygon

[kafitzgerald]

I'm also seeing this error with cartopy (version 0.22.0) and shapely version 2 and above (dropping down to version 1.8.x allows things to work properly).

In this particular case it's coming from Xarray DataArray.plot which uses pcolormesh and pcolor

I can try to dig into this a bit more and/or put together a MRE, but wanted to at least log this here in case it helps other users or devs.

Details

``` --------------------------------------------------------------------------- TypeError Traceback (most recent call last) Cell In[7], line 13 10 tas_present = test.sel(time="2014-07").squeeze() 12 # plot the model data ---> 13 (tas_present - 273.15).plot( 14 ax=ax_present, 15 x="lon", 16 y="lat", 17 transform=ccrs.PlateCarree(), 18 vmin=-10, 19 vmax=30, 20 cmap="magma" 21 #robust=True 22 ) 23 ax_present.coastlines() 24 ax_present.set_title("July 2014")

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/xarray/plot/accessor.py:48, in DataArrayPlotAccessor.call(self, **kwargs)
46 @functools.wraps(dataarray_plot.plot, assigned=("doc", "annotations"))
47 def call(self, **kwargs) -> Any:
---> 48 return dataarray_plot.plot(self._da, **kwargs)

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/xarray/plot/dataarray_plot.py:309, in plot(darray, row, col, col_wrap, ax, hue, subplot_kws, **kwargs)
305 plotfunc = hist
307 kwargs["ax"] = ax
--> 309 return plotfunc(darray, **kwargs)

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/xarray/plot/dataarray_plot.py:1601, in _plot2d..newplotfunc(failed resolving arguments)
1597 raise ValueError("plt.imshow's aspect kwarg is not available in xarray")
1599 ax = get_axis(figsize, size, aspect, ax, **subplot_kws)
-> 1601 primitive = plotfunc(
1602 xplt,
1603 yplt,
1604 zval,
1605 ax=ax,
1606 cmap=cmap_params["cmap"],
1607 vmin=cmap_params["vmin"],
1608 vmax=cmap_params["vmax"],
1609 norm=cmap_params["norm"],
1610 **kwargs,
1611 )
1613 # Label the plot with metadata
1614 if add_labels:

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/xarray/plot/dataarray_plot.py:2309, in pcolormesh(x, y, z, ax, xscale, yscale, infer_intervals, **kwargs)
2306 y = _infer_interval_breaks(y, axis=0, scale=yscale)
2308 ax.grid(False)
-> 2309 primitive = ax.pcolormesh(x, y, z, **kwargs)
2311 # by default, pcolormesh picks "round" values for bounds
2312 # this results in ugly looking plots with lots of surrounding whitespace
2313 if not hasattr(ax, "projection") and x.ndim == 1 and y.ndim == 1:
2314 # not a cartopy geoaxis

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/cartopy/mpl/geoaxes.py:315, in _add_transform..wrapper(self, *args, **kwargs)
310 raise ValueError(f'Invalid transform: Spherical {func.name} '
311 'is not supported - consider using '
312 'PlateCarree/RotatedPole.')
314 kwargs['transform'] = transform
--> 315 return func(self, *args, **kwargs)

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/cartopy/mpl/geoaxes.py:1783, in GeoAxes.pcolormesh(self, *args, **kwargs)
1781 result = super().pcolormesh(*args, **kwargs)
1782 # Wrap the quadrilaterals if necessary
-> 1783 result = self._wrap_quadmesh(result, **kwargs)
1784 # Re-cast the QuadMesh as a GeoQuadMesh to enable future wrapping
1785 # updates to the collection as well.
1786 result.class = cartopy.mpl.geocollection.GeoQuadMesh

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/cartopy/mpl/geoaxes.py:1965, in GeoAxes._wrap_quadmesh(self, collection, **kwargs)
1955 if _MPL_VERSION.release[:2] < (3, 8):
1956 # We will add the original data mask in later to
1957 # make sure that set_array can work in future
(...)
1962 # fill in the proper data later with set_array()
1963 # calls.
1964 pcolor_zeros = np.ma.array(np.zeros(C.shape), mask=pcolor_mask)
-> 1965 pcolor_col = self.pcolor(coords[..., 0], coords[..., 1],
1966 pcolor_zeros, zorder=zorder,
1967 **kwargs)
1969 # The pcolor_col is now possibly shorter than the
1970 # actual collection, so grab the masked cells
1971 pcolor_col.set_array(pcolor_data[mask].ravel())

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/cartopy/mpl/geoaxes.py:315, in _add_transform..wrapper(self, *args, **kwargs)
310 raise ValueError(f'Invalid transform: Spherical {func.name} '
311 'is not supported - consider using '
312 'PlateCarree/RotatedPole.')
314 kwargs['transform'] = transform
--> 315 return func(self, *args, **kwargs)

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/cartopy/mpl/geoaxes.py:2012, in GeoAxes.pcolor(self, *args, **kwargs)
2009 result = super().pcolor(*args, **kwargs)
2011 # Update the datalim for this pcolor.
-> 2012 limits = result.get_datalim(self.transData)
2013 self.update_datalim(limits)
2015 self.autoscale_view()

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/matplotlib/collections.py:266, in Collection.get_datalim(self, transData)
263 return transforms.Bbox.null()
265 if not transform.is_affine:
--> 266 paths = [transform.transform_path_non_affine(p) for p in paths]
267 # Don't convert transform to transform.get_affine() here because
268 # we may have transform.contains_branch(transData) but not
269 # transforms.get_affine().contains_branch(transData). But later,
270 # be careful to only apply the affine part that remains.
272 if any(transform.contains_branch_seperately(transData)):
273 # collections that are just in data units (like quiver)
274 # can properly have the axes limits set by their shape +
275 # offset. LineCollections that have no offsets can
276 # also use this algorithm (like streamplot).

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/matplotlib/collections.py:266, in (.0)
263 return transforms.Bbox.null()
265 if not transform.is_affine:
--> 266 paths = [transform.transform_path_non_affine(p) for p in paths]
267 # Don't convert transform to transform.get_affine() here because
268 # we may have transform.contains_branch(transData) but not
269 # transforms.get_affine().contains_branch(transData). But later,
270 # be careful to only apply the affine part that remains.
272 if any(transform.contains_branch_seperately(transData)):
273 # collections that are just in data units (like quiver)
274 # can properly have the axes limits set by their shape +
275 # offset. LineCollections that have no offsets can
276 # also use this algorithm (like streamplot).

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/matplotlib/transforms.py:2439, in CompositeGenericTransform.transform_path_non_affine(self, path)
2437 return path
2438 elif not self._a.is_affine and self._b.is_affine:
-> 2439 return self._a.transform_path_non_affine(path)
2440 else:
2441 return self._b.transform_path_non_affine(
2442 self._a.transform_path(path))

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/cartopy/mpl/geoaxes.py:186, in InterProjectionTransform.transform_path_non_affine(self, src_path)
182 geoms = cpatch.path_to_geos(src_path,
183 getattr(self, 'force_path_ccw', False))
185 for geom in geoms:
--> 186 proj_geom = self.target_projection.project_geometry(
187 geom, self.source_projection)
188 transformed_geoms.append(proj_geom)
190 if not transformed_geoms:

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/cartopy/crs.py:817, in Projection.project_geometry(self, geometry, src_crs)
815 if not method_name:
816 raise ValueError(f'Unsupported geometry type {geom_type!r}')
--> 817 return getattr(self, method_name)(geometry, src_crs)

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/cartopy/crs.py:972, in Projection._project_polygon(self, polygon, src_crs)
968 rings.extend(self._attach_lines_to_boundary(multi_lines, is_ccw))
970 # Resolve all the inside vs. outside rings, and convert to the
971 # final MultiPolygon.
--> 972 return self._rings_to_multi_polygon(rings, is_ccw)

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/cartopy/crs.py:1233, in Projection._rings_to_multi_polygon(self, rings, is_ccw)
1230 polygon_bits.append(polygon)
1232 if polygon_bits:
-> 1233 multi_poly = sgeom.MultiPolygon(polygon_bits)
1234 else:
1235 multi_poly = sgeom.MultiPolygon()

File ~/miniconda3/envs/geocat-examples/lib/python3.11/site-packages/shapely/geometry/multipolygon.py:79, in MultiPolygon.new(self, polygons)
77 ob = polygons[i]
78 if not isinstance(ob, polygon.Polygon):
---> 79 shell = ob[0]
80 if len(ob) > 1:
81 holes = ob[1]

TypeError: 'GeometryCollection' object is not subscriptable

</details>

[guidoca]

We are getting the same issue. Somehow a GeometryCollection appears. Modifying rings_to_multipolygon to skip any GeometryCollections fixes the issue.

It's probably the result of a weird geometry in the underlying contours, but impossible to tell exactly what when working with very big datasets.

I would suggest adding a mechanism to skip GeometrieCollection if present within polygon_bits and throw a warning, or recursively call rings_to_multipolygon with the GeometryCollection parts ?

[ghiggi]

Hi all,

I also encoutered this bug multiple times recently while working with pyresample and gpm-api.

I would like to report here below two very simple reproducible example:

TypeError: 'MultiPolygon' object is not subscriptable

import cartopy.crs as ccrs
import matplotlib.pyplot as plt
crs_proj = ccrs.LambertAzimuthalEqualArea(central_latitude=-90)
fig, ax = plt.subplots(1, 1, subplot_kw={"projection": crs_proj})
ax.add_feature(cartopy.feature.OCEAN)

TypeError: 'GeometryCollection' object is not subscriptable

import cartopy.crs as ccrs
import matplotlib.pyplot as plt
crs_proj = ccrs.LambertAzimuthalEqualArea(central_latitude=-30)
fig, ax = plt.subplots(1, 1, subplot_kw={"projection": crs_proj})
ax.add_feature(cartopy.feature.OCEAN)

[rcomer]

@ghiggi thanks for the report. I can reproduce those error with Cartopy 0.24.0, though with our main development branch I get a different error:

shapely.errors.GEOSException: TopologyException: side location conflict at -12484110.185528276 1210758.1658385277. This can occur if the input geometry is invalid.

[rcomer]

The code from the OP now gives me this against main:

shapely.errors.GEOSException: TopologyException: unable to assign free hole to a shell at -9601843.5095015578 -6188385.5877522295

[greglucas]

@rcomer, I think your work on the patch projections has greatly improved the situation. I wonder if we need to look at @kdpenner's work again for this since the holes/topology work seems related.
#1739

[rcomer]

If I do

import matplotlib.pyplot as plt
import cartopy.crs as ccrs
import shapely.geometry as sgeom

sudo_ocean = sgeom.Polygon([(-180, -80), (180, -80), (180, 90), (-180, 90)],
                           [[(-50, 60), (-50, 80), (0, 80), (0, 60)],
                            [(-50, 81), (-50, 85), (0, 85), (0, 81)]])

crs_proj = ccrs.LambertAzimuthalEqualArea(central_latitude=-90)
fig, ax = plt.subplots(1, 1, subplot_kw={"projection": crs_proj})
ax.add_geometries(sudo_ocean, crs=ccrs.PlateCarree())
    
plt.show()

I get the "side location conflict" error. It's because the two interiors are touching each other after projection. Two valid polygons can make an invalid multipolygon if they touch along a line. I have a patch for this.

If I do

import matplotlib.pyplot as plt
import cartopy.crs as ccrs
import shapely.geometry as sgeom

sudo_ocean = sgeom.Polygon([(-180, -80), (180, -80), (180, 90), (-180, 90)],
                           [[(-50, 81), (-50, 85), (0, 85), (0, 81)]])

crs_proj = ccrs.LambertAzimuthalEqualArea(central_latitude=-30)
fig, ax = plt.subplots(1, 1, subplot_kw={"projection": crs_proj})
ax.add_geometries(sudo_ocean, crs=ccrs.PlateCarree())
    
plt.show()

I get the "unable to assign free hole to a shell" error.

[rcomer]

In fact the -30 latitude is great for breaking things!

import matplotlib.pyplot as plt
import cartopy.crs as ccrs
import shapely.geometry as sgeom

sudo_ocean = sgeom.Polygon([(-180, -80), (180, -80), (180, 90), (-180, 90)])

crs_proj = ccrs.LambertAzimuthalEqualArea(central_latitude=-30)
fig, ax = plt.subplots(1, 1, subplot_kw={"projection": crs_proj})
ax.add_geometries(sudo_ocean, crs=ccrs.PlateCarree())
    
plt.show()

TypeError: 'GeometryCollection' object is not subscriptable

Edit: the root of the problem here seems pretty deep. The initial projection creates a self-intersecting line

Which then gets attached to the boundary here

cartopy/lib/cartopy/crs.py

Line 977 in 824cb14

rings.extend(self._attach_lines_to_boundary(multi_lines, is_ccw))