I've run into an issue pickling a datetime.time subclass in PyPy3. I believe it arises because PyPy uses the pure Python implementation of time and time.__reduce_ex__() returns (time, ...) on this line (https://github.com/python/cpython/blob/044a1048ca93d466965afc027b91a5a9eb9ce23c/Lib/datetime.py#L1551) rather than (self.__class__, ...) as it does for datetime.datetime (and in datetime.date.__reduce__()). So when pickle creates the dump it uses the time class rather than my subclass.

Code demonstrating the issue; the CTimeFoo class is pickled correctly, but TimeFoo isn't.


import builtins
from _datetime import time as ctime

original_importer = builtins.__import__

def my_importer(name, globals, locals, fromlist, level):
    if name == '_datetime':
        raise ImportError

    return original_importer(name, globals, locals, fromlist, level)

builtins.__import__ = my_importer

import datetime

builtins.__import__ = original_importer

import pickle


class CTimeFoo(ctime): pass
class TimeFoo(datetime.time): pass
class DateFoo(datetime.date): pass


if __name__ == "__main__":
    t = DateFoo(2001, 2, 3) 
    d = pickle.dumps(t)  # OK
    print(d)
    # b'\x80\x04\x95#\x00\x00\x00\x00\x00\x00\x00\x8c\x08__main__\x94\x8c\x07DateFoo\x94\x93\x94C\x04\x07\xd1\x02\x03\x94\x85\x94R\x94.'
    t = pickle.loads(d)

    t = CTimeFoo(1, 2, 3)  
    d = pickle.dumps(t)  # OK
    print(d)
    # b'\x80\x04\x95&\x00\x00\x00\x00\x00\x00\x00\x8c\x08__main__\x94\x8c\x08CTimeFoo\x94\x93\x94C\x06\x01\x02\x03\x00\x00\x00\x94\x85\x94R\x94.'
    t = pickle.loads(d)

    t = TimeFoo(1, 2, 3)
    d = pickle.dumps(t)  # :(
    print(d)
    # b'\x80\x04\x95"\x00\x00\x00\x00\x00\x00\x00\x8c\x08datetime\x94\x8c\x04time\x94\x93\x94C\x06\x01\x02\x03\x00\x00\x00\x94\x85\x94R\x94.'
    t = pickle.loads(d)

New changeset c304c9a7efa8751b5bc7526fa95cd5f30aac2b92 by scaramallion in branch 'master':
bpo-41966: Fix pickling pure datetime.time subclasses (GH-22731)
https://github.com/python/cpython/commit/c304c9a7efa8751b5bc7526fa95cd5f30aac2b92

New changeset a055ced9d43630cadc3c1d5edab0884f2c5131ea by Miss Skeleton (bot) in branch '3.9':
bpo-41966: Fix pickling pure datetime.time subclasses (GH-22731) (GH-22747)
https://github.com/python/cpython/commit/a055ced9d43630cadc3c1d5edab0884f2c5131ea

New changeset 1040299e9283609f3de0f6e32a0d43458fe7f4f6 by Miss Skeleton (bot) in branch '3.8':
bpo-41966: Fix pickling pure datetime.time subclasses (GH-22731) (GH-22748)
https://github.com/python/cpython/commit/1040299e9283609f3de0f6e32a0d43458fe7f4f6