Pyomo Compatibility with Python 3.11

Question

Is there a known compatibility issue with pyomo and python 3.11?

Just trying out the latest/greatest python release and importing pyomo is failing with pyomo v 6.4.2:

Python 3.11.0 (v3.11.0:deaf509e8f, Oct 24 2022, 14:43:23) [Clang 13.0.0 (clang-1300.0.29.30)] on darwin
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>>> from pyomo.environ import *
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/pyomo/environ/__init__.py", line 79, in <module>
    _import_packages()
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/pyomo/environ/__init__.py", line 61, in _import_packages
    _do_import(pname)
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/pyomo/environ/__init__.py", line 16, in _do_import
    importlib.import_module(pkg_name)
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/pyomo/core/__init__.py", line 43, in <module>
    from pyomo.core import expr, util, kernel
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/pyomo/core/util.py", line 21, in <module>
    from pyomo.core.base.var import Var
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/pyomo/core/base/__init__.py", line 34, in <module>
    from pyomo.core.base.label import (CuidLabeler,
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/pyomo/core/base/label.py", line 19, in <module>
    from pyomo.core.base.componentuid import ComponentUID
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/pyomo/core/base/componentuid.py", line 25, in <module>
    from pyomo.core.base.reference import Reference
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/pyomo/core/base/reference.py", line 17, in <module>
    from pyomo.core.base.set import SetOf, OrderedSetOf, _SetDataBase
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/pyomo/core/base/set.py", line 4208, in <module>
    DeclareGlobalSet(_AnySet(
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/pyomo/core/base/set.py", line 4199, in DeclareGlobalSet
    _set.__class__.__setstate__(_set, obj.__getstate__())
                                      ^^^^^^^^^^^^^^^^^^
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/pyomo/core/base/component.py", line 787, in __getstate__
    state = _base.__getstate__()
            ^^^^^^^^^^^^^^^^^^^^
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/pyomo/core/base/indexed_component.py", line 316, in __getstate__
    state = super(IndexedComponent, self).__getstate__()
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/pyomo/core/base/component.py", line 471, in __getstate__
    state[key] = val
    ~~~~~^^^^^
TypeError: 'tuple' object does not support item assignment
>>> 

Pyomo Version check:

~ % pip3 show pyomo
Name: Pyomo
Version: 6.4.2
Summary: Pyomo: Python Optimization Modeling Objects
Home-page: http://pyomo.org
Author: 
Author-email: 
License: BSD
Location: /Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages
Requires: ply
Required-by: 
~ % 

Answer 1

Pyomo 6.4.2 isn't compatible with python 3.11. You need to update to 6.4.3, which was released on 28th November 2022.

Previous answer - before 6.4.3 update

Verion 6.4.2 does some stuff with pickle and the __getstate__/__setstate__ functions. However, Python 3.11 introduced a default implementation for these functions that does not match Pyomo's expectations. So the whole thing falls over.

See this note on the new default implementation for __getstate__.

Classes can further influence how their instances are pickled by overriding the method getstate(). It is called and the returned object is pickled as the contents for the instance, instead of a default state. There are several cases:

• For a class that has no instance __dict__ and no __slots__, the default state is None.

• For a class that has an instance __dict__ and no __slots__, the default state is self.__dict__.

• For a class that has an instance __dict__ and __slots__, the default state is a tuple consisting of two dictionaries: self.__dict__, and a dictionary mapping slot names to slot values. Only slots that have a value are included in the latter.

• For a class that has __slots__ and no instance __dict__, the default state is a tuple whose first item is None and whose second item is a dictionary mapping slot names to slot values described in the previous bullet.

Changed in version 3.11: Added the default implementation of the __getstate__() method in the object class.

In the v6.4.2 code base you can see it does a check to see if __getstate__ is implemented or not. https://github.com/Pyomo/pyomo/blob/6.4.2/pyomo/core/base/component.py#L467

In the main branch, this code has recently been changed. And there is a recent commit saying that the code is now 3.11 compatible. So just hang tight, and wait for the new version to be release.

Or if you really cannot wait and just want to experiment, then install the development version of 6.4.3 with git:

eg.

pip install git+https://github.com/Pyomo/pyomo.git@main

NB. Obviously, you'll need git installed to be able to do this. And do not use this to install pyomo for production code. This is code that is under development and has not yet been released.