Deprecation Warning for Python 3.14

[stammler]

I'm currently getting a DeprecationWarning in my project originating from dill:

python3.13/site-packages/dill/_dill.py:452: DeprecationWarning: Pickle, copy, and deepcopy support will be removed from itertools in Python 3.14.
    obj = StockUnpickler.load(self)

Potentially related to #692.

[mmckerns]

Can you provide code that reproduces what you are seeing? The DeprecationWarning is definitely related to python's builtin support for pickling itertools.

[stammler]

Sorry for the delay! It took me a while to identify the exact issue in our project.

It seems like the warning is associated with itertools.cycle. We have a spinner class in our project to indicate to the user that the code is still executing.

Here is a minimum working example.

# file: test.py
#!/usr/bin/python3

import dill
from itertools import cycle
from pathlib import Path
import time

dill.detect.trace(True)


class Spinner(object):

    def __init__(self, charlist=["⠉", "⠘", "⠒", "⠃"]):
        super().__init__()
        self._cycle = cycle(charlist)

    def __call__(self):
        return next(self._cycle)


if __name__ == "__main__":

    # Spin for three seconds
    spinner = Spinner()
    print('\033[?25l', end="")
    for i in range(30):
        char = spinner()
        L = len(char)
        print(char, end="")
        time.sleep(.1)
        print(f"\r{L*''}\r", end="")
    print('\033[?25h', end="")
    
    # Dump spinner
    filename = Path("spinner.dump")
    with open("spinner.dump", "wb") as file:
        dill.dump(spinner, file)
    # Delete file
    filename.unlink()

Running this file with python -X dev test.py will produce the DeprecationWarning.

[mmckerns]

Ok, thanks for the test case. My thought is this: dill should not throw a DeprecationWarning unless the user tries to pickle anything from itertools. Basically, if itertools isn't required for any registered pickling functions, then this ticket should be closed. If it is, then that warning should be suppressed. #692 should stand regardless until there's a dill solution to pickling itertools going forward.

[stammler]

Ok, so I think this can be closed as it is covered with #692.

In general, since we could achive our use case in other ways without using itertools, would you recommend to drop it, or do you think dill will still support it by the time of 3.14?

[mmckerns]

The plan is to support pickling of itertools for 3.14. The module is implemented in itertoolsmodule.c, and the functions supporting pickling were removed. So, I expect it may be possible to do something with ctypes if only the python functions were removed.