RecursionError when loading file in python 3.14 #6762
Description
🐛 Bug Report
Whenever you try and load a file (at least for NetCDF files) in iris under python 3.14, the process crashes with a RecursionError.
How To Reproduce
Steps to reproduce the behaviour:
-
Create a conda environment with python 3.14 and iris with
conda create -n py314-iris python iris -
Save the following code into a file called
test.py:#!/usr/bin/env python3 """Test script for python 3.14 support in iris.""" import sys import iris print(f"Using python {sys.version}") print(f"Using iris {iris.__version__}") cubes = iris.load("air_temp.nc") print(cubes)
-
Download air_temp.nc and put it in the same directory as the
test.pyscript. -
Activate the conda environment with
conda activate py314-iris -
Run the script with
python test.py -
Observe the
RecursionError.
Expected behaviour
Iris successfully loads the file, and doesn't crash.
Environment
- OS & Version: Red Hat Enterprise Linux 9.6 (Plow)
- Iris Version: 3.13.1 (from conda-forge)
- Python Version: 3.14.0 | packaged by conda-forge | (main, Oct 22 2025, 23:24:08) [GCC 14.3.0]
Additional context
The following traceback lines are repeated many times.
File "/home/users/james.frost/.conda/envs/py314-iris/lib/python3.14/copy.py", line 138, in deepcopy
y = copier(memo)
File "/home/users/james.frost/.conda/envs/py314-iris/lib/python3.14/site-packages/iris/coords.py", line 2730, in __deepcopy__
new_coord = copy.deepcopy(super(), memo)
File "/home/users/james.frost/.conda/envs/py314-iris/lib/python3.14/copy.py", line 157, in deepcopy
y = _reconstruct(x, memo, *rv)
File "/home/users/james.frost/.conda/envs/py314-iris/lib/python3.14/copy.py", line 234, in _reconstruct
y = func(*args)
File "/home/users/james.frost/.conda/envs/py314-iris/lib/python3.14/copy.py", line 233, in <genexpr>
args = (deepcopy(arg, memo) for arg in args)
~~~~~~~~^^^^^^^^^^^
File "/home/users/james.frost/.conda/envs/py314-iris/lib/python3.14/copy.py", line 138, in deepcopy
y = copier(memo)
File "/home/users/james.frost/.conda/envs/py314-iris/lib/python3.14/site-packages/iris/coords.py", line 2730, in __deepcopy__
new_coord = copy.deepcopy(super(), memo)
File "/home/users/james.frost/.conda/envs/py314-iris/lib/python3.14/copy.py", line 157, in deepcopy
y = _reconstruct(x, memo, *rv)
File "/home/users/james.frost/.conda/envs/py314-iris/lib/python3.14/copy.py", line 234, in _reconstruct
y = func(*args)
File "/home/users/james.frost/.conda/envs/py314-iris/lib/python3.14/copy.py", line 233, in <genexpr>
args = (deepcopy(arg, memo) for arg in args)
~~~~~~~~^^^^^^^^^^^
File "/home/users/james.frost/.conda/envs/py314-iris/lib/python3.14/copy.py", line 138, in deepcopy
y = copier(memo)
RecursionError: maximum recursion depth exceeded
Please see log.txt for the full traceback.