pydantic import error i QGIS

[biglimp]

A user gets this error upgrading UMEP. Something related to pydantic as far as I can see.

supy version: 2026.1.28rc1

Any ideas?

Couldn't load plugin 'UMEP' due to an error when calling its classFactory() method

ImportError: cannot import name 'validate_core_schema' from 'pydantic_core' (C:\OSGeo4W\apps\Python312\Lib\site-packages\pydantic_core\__init__.py)
Traceback (most recent call last):
File "C:\OSGeo4W/apps/qgis/./python\qgis\utils.py", line 478, in _startPlugin
plugins[packageName] = package.classFactory(iface)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users/gusbloomi/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\UMEP\__init__.py", line 42, in classFactory
from .UMEP import UMEP
File "C:\OSGeo4W/apps/qgis/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users/gusbloomi/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\UMEP\UMEP.py", line 68, in
from .suews_database_manager.suews_database_manager import suews_database_manager
File "C:\OSGeo4W/apps/qgis/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users/gusbloomi/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\UMEP\suews_database_manager\suews_database_manager.py", line 53, in
from .utilities.database_functions import read_DB
File "C:\OSGeo4W/apps/qgis/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users/gusbloomi/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\UMEP\suews_database_manager\utilities\database_functions.py", line 8, in
from [supy.data](http://supy.data/)_model.schema.publisher import generate_json_schema
File "C:\OSGeo4W/apps/qgis/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\gusbloomi\AppData\Roaming\Python\Python312\site-packages\supy\data_model\__init__.py", line 15, in
from .core import (
File "C:\OSGeo4W/apps/qgis/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\gusbloomi\AppData\Roaming\Python\Python312\site-packages\supy\data_model\core\__init__.py", line 8, in
from .config import SUEWSConfig, init_config_from_yaml
File "C:\OSGeo4W/apps/qgis/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\gusbloomi\AppData\Roaming\Python\Python312\site-packages\supy\data_model\core\config.py", line 14, in
from pydantic import (
File "C:\OSGeo4W/apps/qgis/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\OSGeo4W\apps\Python312\Lib\site-packages\pydantic\__init__.py", line 435, in __getattr__
module = import_module(module_name, package=package)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\OSGeo4W\apps\Python312\Lib\importlib\__init__.py", line 90, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\OSGeo4W\apps\Python312\Lib\site-packages\pydantic\[main.py](http://main.py/)", line 36, in
from ._internal import (
File "C:\OSGeo4W/apps/qgis/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\OSGeo4W\apps\Python312\Lib\site-packages\pydantic\_internal\_decorators.py", line 18, in
from ._core_utils import get_type_ref
File "C:\OSGeo4W/apps/qgis/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\OSGeo4W\apps\Python312\Lib\site-packages\pydantic\_internal\_core_utils.py", line 9, in
from pydantic_core import validate_core_schema as _validate_core_schema
ImportError: cannot import name 'validate_core_schema' from 'pydantic_core' (C:\OSGeo4W\apps\Python312\Lib\site-packages\pydantic_core\__init__.py)


Python version: 3.12.11 (main, Jun 17 2025, 13:41:12) [MSC v.1943 64 bit (AMD64)]
QGIS version: 3.44.3-Solothurn Solothurn, 1d1d67e9edd

Python Path:
C:\Users\gusbloomi\AppData\Roaming\Python\Python312\site-packages
C:\Users\gusbloomi\AppData\Roaming\Python\Python312\site-packages
C:\Users\gusbloomi\AppData\Roaming\Python\Python312\site-packages
C:\Users\gusbloomi\AppData\Roaming\Python\Python312\site-packages
C:\Users\gusbloomi\AppData\Roaming\Python\Python312\site-packages
C:\Users\gusbloomi\AppData\Roaming\Python\Python312\site-packages
C:/OSGeo4W/apps/qgis/./python
C:/Users/gusbloomi/AppData/Roaming/QGIS/QGIS3\profiles\default/python
C:/Users/gusbloomi/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins
C:/OSGeo4W/apps/qgis/./python/plugins
C:\OSGeo4W\apps\grass\grass84\etc\python
C:\WINDOWS\system32
C:\OSGeo4W\bin\[python312.zip](http://python312.zip/)
C:\OSGeo4W\apps\Python312\DLLs
C:\OSGeo4W\apps\Python312\Lib
C:\OSGeo4W\bin
C:\Users\gusbloomi\AppData\Roaming\Python\Python312\site-packages
C:\OSGeo4W\apps\Python312
C:\OSGeo4W\apps\Python312\Lib\site-packages
C:\OSGeo4W\apps\Python312\Lib\site-packages\win32
C:\OSGeo4W\apps\Python312\Lib\site-packages\win32\lib
C:\OSGeo4W\apps\Python312\Lib\site-packages\Pythonwin
C:/Users/gusbloomi/AppData/Roaming/QGIS/QGIS3\profiles\default/python
C:\OSGeo4W\apps\Python312\Lib\site-packages\setuptools\_vendor
D:/GU

[sunt05]

Hi @biglimp — this is a pydantic version conflict between OSGeo4W's system packages and what supy needs.

What's happening

OSGeo4W ships its own pydantic and pydantic_core in C:\OSGeo4W\apps\Python312\Lib\site-packages\. When the user installed supy with pip install --user supy, pip saw the existing system pydantic and considered the dependency satisfied — so it never installed a newer version to user site-packages. But supy now uses pydantic features that require pydantic-core ≥ 2.33 (specifically validate_core_schema), and the OSGeo4W version is older than that.

Fix for the user

From the OSGeo4W shell:

python -m pip install --user --upgrade pydantic pydantic-core

This installs newer versions to user site-packages, which take precedence over the system ones.

Longer-term fix

We should pin pydantic>=2.12 in supy's pyproject.toml so pip knows to upgrade rather than accepting the old system version. I'll sort that out on the SUEWS side.