Import error in QGIS4 env.

[biglimp]

I am getting an import error in QGIS4 env.

from supy import SUEWSSimulation
Traceback (most recent call last):
  File "<input>", line 1, in <module>
ImportError: cannot import name 'SUEWSSimulation' from 'supy' (C:\Users\xlinfr\AppData\Roaming\Python\Python312\site-packages\supy\__init__.py)

Version and platform

• SUEWS/SuPy version: 2026.1.28rc1
• OS: Windows 11
• Python version (if applicable): 3.12

Here is the list of python packages in the updated env:

Package                       Version
----------------------------- ------------
affine                        2.4.0
alabaster                     1.0.0
annotated-types               0.7.0
anyio                         4.12.1
argon2-cffi                   25.1.0
argon2-cffi-bindings          25.1.0
asteval                       1.0.8
astpretty                     3.0.0
asttokens                     3.0.1
async-lru                     2.1.0
atmosp                        0.2.16
attrs                         25.4.0
babel                         2.18.0
beautifulsoup4                4.14.3
bleach                        6.3.0
cdsapi                        0.7.7
certifi                       2026.1.4
cffi                          2.0.0
cftime                        1.6.5
chardet                       7.1.0
charset-normalizer            3.4.4
click                         8.3.1
click-plugins                 1.1.1.2
cligj                         0.7.2
colorama                      0.4.6
comm                          0.2.3
contourpy                     1.3.3
cycler                        0.12.1
debugpy                       1.8.20
decorator                     5.2.1
defusedxml                    0.7.1
dill                          0.4.1
docutils                      0.22.4
duckdb                        1.4.4
ecmwf-datastores-client       0.4.2
et_xmlfile                    2.0.0
executing                     2.2.1
ExifRead                      3.5.1
f90nml                        1.5.0
fastjsonschema                2.21.2
fonttools                     4.61.1
future                        1.0.0
GDAL                          3.12.2
geographiclib                 2.1
geopandas                     1.1.2
h11                           0.16.0
httpcore                      1.0.9
httplib2                      0.31.2
httpx                         0.28.1
idna                          3.11
imagesize                     2.0.0
ipykernel                     7.2.0
ipython                       9.10.0
ipython_pygments_lexers       1.1.1
ipywidgets                    8.1.8
JayDeBeApi                    1.2.3
jedi                          0.19.2
Jinja2                        3.1.6
joblib                        1.5.3
jpype1                        1.6.0
json5                         0.13.0
jsonschema                    4.26.0
jsonschema-specifications     2025.9.1
jupyter                       1.1.1
jupyter_client                8.8.0
jupyter-console               6.6.3
jupyter_core                  5.9.1
jupyter-events                0.12.0
jupyter-lsp                   2.3.0
jupyter_server                2.17.0
jupyter_server_terminals      0.5.4
jupyterlab                    4.5.4
jupyterlab_pygments           0.3.0
jupyterlab_server             2.28.0
jupyterlab_widgets            3.0.15
kiwisolver                    1.4.9
llvmlite                      0.42.0
lmfit                         1.3.4
lxml                          6.0.2
markdown-it-py                4.0.0
MarkupSafe                    3.0.3
matplotlib                    3.10.8
matplotlib-inline             0.2.1
mdurl                         0.1.2
mistune                       3.2.0
mock                          5.2.0
multiurl                      0.3.7
narwhals                      2.16.0
nbclient                      0.10.4
nbconvert                     7.17.0
nbformat                      5.10.4
nest-asyncio                  1.6.0
netCDF4                       1.7.4
networkx                      3.6.1
nose2                         0.15.1
notebook                      7.5.3
notebook_shim                 0.2.4
numba                         0.59.0
numexpr                       2.14.1
numpy                         1.26.4
openpyxl                      3.1.5
OWSLib                        0.35.0
packaging                     25.0
pandas                        3.0.1
pandocfilters                 1.5.1
parso                         0.8.6
pb-tool                       3.1.0
pillow                        12.1.1
pip                           26.0.1
platformdirs                  4.9.2
plotly                        6.5.2
ply                           3.11
prometheus_client             0.24.1
prompt_toolkit                3.0.52
psutil                        7.2.2
psycopg                       3.3.3
psycopg2                      2.9.11
pure_eval                     0.2.3
pyarrow                       23.0.1
pycparser                     3.0
pydantic                      2.12.5
pydantic_core                 2.41.5
Pygments                      2.19.2
pyodbc                        5.3.0
pyogrio                       0.12.1
PyOpenGL                      3.1.10
pyparsing                     3.3.2
PyPDF2                        3.0.1
pypiwin32                     223
pyproj                        3.7.2
PyQt6                         6.10.2
PyQt6_sip                     13.11.0
pyserial                      3.5
python-dateutil               2.9.0.post0
python-json-logger            4.0.0
pytz                          2025.2
pywin32                       311
pywinpty                      3.0.3
PyYAML                        6.0.3
pyzmq                         27.1.0
rasterio                      1.4.3
referencing                   0.37.0
remotior_sensus               0.6.2
reportlab                     4.4.10
requests                      2.32.5
rfc3339_validator             0.1.4
rfc3986_validator             0.1.1
rich                          14.3.3
rioxarray                     0.19.0
roman-numerals                4.1.0
rpds-py                       0.30.0
scikit-learn                  1.8.0
scipy                         1.17.0
seaborn                       0.13.2
Send2Trash                    2.1.0
setuptools                    82.0.0
shapely                       2.1.2
simplejson                    3.20.2
sip                           6.15.1
six                           1.17.0
snowballstemmer               3.0.1
soupsieve                     2.8.3
Sphinx                        9.1.0
sphinxcontrib-applehelp       2.0.0
sphinxcontrib-devhelp         2.0.0
sphinxcontrib-htmlhelp        2.1.0
sphinxcontrib-jsmath          1.0.1
sphinxcontrib-qthelp          2.0.0
sphinxcontrib-serializinghtml 2.0.0
stack_data                    0.6.3
supy                          2026.1.28rc1
target-py                     0.1.1
terminado                     0.18.1
threadpoolctl                 3.6.0
tokenize_rt                   6.2.0
tornado                       6.5.4
tqdm                          4.67.3
traitlets                     5.14.3
typing_extensions             4.15.0
typing-inspection             0.4.2
tzdata                        2025.3
tzfpy                         1.1.3
umep-reqs                     2.9
uncertainties                 3.2.3
urllib3                       2.6.3
uwg                           5.8.13
wcwidth                       0.6.0
webencodings                  0.5.1
websocket-client              1.9.0
widgetsnbextension            4.0.15
wxPython                      4.2.4
xarray                        2026.2.0
xlrd                          2.0.2
xlwt                          1.3.0

[sunt05]

Thanks for reporting this, @biglimp.

The 2026.1.28rc1 build was a special pre-release targeting UMEP in the QGIS 3 environment — it was compiled against NumPy 1.x. Now that QGIS 4 has moved to a NumPy 2.x ecosystem, that rc1 wheel is no longer compatible: the compiled Fortran extension fails to load, which causes the SUEWSSimulation import to silently fail.

Could you try installing the proper release version instead?

pip install supy==2026.1.28

This version is built against NumPy 2.x and should work correctly in QGIS 4. You may also need to ensure NumPy 2.x is installed in the environment (pip install "numpy>=2.0"), since your package list shows 1.26.4.

[sunt05]

Also, I'll update the UMEP requirements package so that the correct supy version is pulled in for both QGIS 3 and QGIS 4 environments. That way it should just work out of the box regardless of which QGIS version you're running.

[sunt05]

Could you let me know once you've tested supy==2026.1.28 in your QGIS 4 environment? If it works, I'll go ahead and update the UMEP requirements package accordingly.

[biglimp]

@sunt05 , trying to understand the numpy version. Could the 1.26 numpy version be forced when I install umep-reqs 2.9 since this requires supy 2026.1.28rc1?

[sunt05]

Exactly.

[biglimp]

Had to reinstall. Tried again with following error messages:

C:\OSGeo4W>python-qgis
Python 3.12.13 (main, Mar  5 2026, 15:14:54) [MSC v.1944 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from supy import SUEWSSimulation
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: cannot import name 'SUEWSSimulation' from 'supy' (C:\OSGeo4W\apps\Python312\Lib\site-packages\supy\__init__.py)
>>> quit()

C:\OSGeo4W>pip list
Package                   Version
------------------------- -----------
annotated-types           0.7.0
asteval                   1.0.8
atmosp                    0.2.16
attrs                     26.1.0
cdsapi                    0.7.7
certifi                   2026.1.4
chardet                   7.4.0.post2
charset-normalizer        3.4.4
click                     8.3.1
colorama                  0.4.6
contourpy                 1.3.3
cycler                    0.12.1
dill                      0.4.1
duckdb                    1.4.4
ecmwf-datastores-client   0.5.0
et_xmlfile                2.0.0
ExifRead                  3.5.1
f90nml                    1.5.0
fonttools                 4.61.1
future                    1.0.0
GDAL                      3.12.2
geographiclib             2.1
geopandas                 1.1.2
httplib2                  0.31.2
idna                      3.11
Jinja2                    3.1.6
joblib                    1.5.3
jsonschema                4.26.0
jsonschema-specifications 2025.9.1
kiwisolver                1.4.9
lmfit                     1.3.4
lxml                      6.0.2
markdown-it-py            4.0.0
MarkupSafe                3.0.3
matplotlib                3.10.8
mdurl                     0.1.2
mock                      5.2.0
multiurl                  0.3.7
narwhals                  2.16.0
networkx                  3.6.1
nose2                     0.15.1
numexpr                   2.14.1
numpy                     2.4.2
openpyxl                  3.1.5
OWSLib                    0.35.0
packaging                 25.0
pandas                    3.0.1
pillow                    12.1.1
pip                       26.0.1
plotly                    6.5.2
ply                       3.11
psycopg                   3.3.3
psycopg2                  2.9.11
pyarrow                   23.0.1
pydantic                  2.12.5
pydantic_core             2.41.5
Pygments                  2.19.2
pyodbc                    5.3.0
pyogrio                   0.12.1
PyOpenGL                  3.1.10
pyparsing                 3.3.2
PyPDF2                    3.0.1
pypiwin32                 223
pyproj                    3.7.2
PyQt6                     6.10.2
PyQt6_sip                 13.11.0
pyserial                  3.5
python-dateutil           2.9.0.post0
pytz                      2025.2
pywin32                   311
PyYAML                    6.0.3
referencing               0.37.0
remotior_sensus           0.6.2
reportlab                 4.4.10
requests                  2.32.5
rich                      14.3.3
rpds-py                   0.30.0
scikit-learn              1.8.0
scipy                     1.17.0
seaborn                   0.13.2
setuptools                82.0.0
shapely                   2.1.2
simplejson                3.20.2
sip                       6.15.1
six                       1.17.0
supy                      2026.1.28
threadpoolctl             3.6.0
tqdm                      4.67.3
typing_extensions         4.15.0
typing-inspection         0.4.2
tzdata                    2025.3
tzfpy                     1.1.3
uncertainties             3.2.3
urllib3                   2.6.3
wxPython                  4.2.4
xlrd                      2.0.2
xlwt                      1.3.0

C:\OSGeo4W>

[sunt05]

Thanks for re-testing, @biglimp. The versions look correct now (supy==2026.1.28 + numpy==2.4.2), so this isn't the NumPy ABI issue I initially suspected. Something else is preventing the Fortran extension from loading in the OSGeo4W environment.

The SUEWSSimulation class is lazy-loaded — if its import chain fails, the error gets silently swallowed. Most likely the compiled supy_driver.pyd can't find its runtime DLLs (libgfortran, libgcc_s, etc.) on the OSGeo4W PATH, or a previous failed import left a broken module cached in sys.modules.

Could you run these diagnostics in the OSGeo4W Python console?

# 1. Check if the Fortran extension loads
try:
    from supy.supy_driver import suews_driver
    print("supy_driver: OK")
except Exception as e:
    print(f"supy_driver: {type(e).__name__}: {e}")

# 2. Check if the import chain works
try:
    from supy.suews_sim import SUEWSSimulation
    print(f"SUEWSSimulation: {SUEWSSimulation}")
except Exception as e:
    print(f"suews_sim: {type(e).__name__}: {e}")

# 3. Check module state
import supy
print(f"__getattr__ defined: {hasattr(type(supy), '__getattr__') or '__getattr__' in dir(supy)}")
print(f"Module keys: {[k for k in sorted(supy.__dict__) if not k.startswith('_')]}")

Step 1 is the critical one — if supy_driver fails to load, that's the root cause and we can work out what DLLs are missing.

[sunt05]

Root cause found

SSH'd into @biglimp's machine via Tailscale to investigate directly. The Fortran extension loads fine — the actual failure is a pyarrow 23 incompatibility with pandas 3.0.1.

What's happening

The OSGeo4W/QGIS 4 environment ships pyarrow==23.0.1, which removed pyarrow.compute.match_substring_regex. When supy loads, _load.py uses pandas.Series.str.contains() with regex on arrow-backed strings, which calls the removed function:

File "supy/_load.py", line 43, in extract_dict_docs
    varInputLines = ser_docs[ser_docs.str.contains("input|in/output")].values
    ...
AttributeError: module 'pyarrow.compute' has no attribute 'match_substring_regex'

This crashes the import chain, and since SUEWSSimulation is lazy-loaded, the error surfaces as a generic ImportError.

Fix

1. Immediate (for @biglimp): downgraded pyarrow on his machine — pip install "pyarrow>=20,<23" — confirmed supy.load_sample_data() works
2. Proper fix in umep-reqs: PR UMEP-dev/umep-reqs#14 — introduces extras for QGIS 3/4 compatibility:
   • pip install umep-reqs[qgis3] → supy==2026.1.28rc1 (NumPy 1.x)
   • pip install umep-reqs[qgis4] → supy==2026.1.28 (NumPy 2.x)
   • pyarrow<23 added to common deps (temporary — the incompatible code path has been refactored on supy master, so this cap drops with the next release)

Note: No change needed in supy's own pyproject.toml on master — the _load.py docstring-parsing code that triggered this has already been replaced by _var_metadata.

Environment on @biglimp's machine

• Python 3.12.13 (OSGeo4W)
• pandas 3.0.1
• pyarrow 23.0.1 (broken) → 22.0.0 (works)
• supy 2026.1.28
• Fortran extension _supy_driver.cp312-win_amd64.pyd loads correctly