document new feature

Author: Christopher Doris

docs/src/releasenotes.md

@@ -4,6 +4,7 @@
 * `Serialization.serialize` can use `dill` instead of `pickle` by setting the env var `JULIA_PYTHONCALL_PICKLE=dill`.
 * `numpy.bool_` can now be converted to `Bool` and other number types.
 * `datetime.timedelta` can now be converted to `Dates.Nanosecond`, `Microsecond`, `Millisecond` and `Second`. This behaviour was already documented.
+* In JuliaCall, the Julia runtime is now properly terminated when Python exits. This means all finalizers should always run.
 
 ## 0.9.20 (2024-05-01)
 * The IPython extension is now automatically loaded upon import if IPython is detected.

pysrc/juliacall/__init__.py

@@ -3,8 +3,6 @@
 
 __version__ = '0.9.20'
 
-import atexit
-
 _newmodule = None
 
 def newmodule(name):
@@ -51,6 +49,7 @@ def backtrace(self):
 CONFIG = {'inited': False}
 
 def init():
+    import atexit
     import os
     import ctypes as c
     import sys
@@ -201,6 +200,8 @@ def args_from_config():
         None if sysimg is None else sysimg.encode('utf8'),
     )
 
+    # call jl_atexit_hook() when python exits to gracefully stop the julia runtime,
+    # including running finalizers for any objects that still exist
     @atexit.register
     def at_jl_exit():
         jl_atexit_hook = lib.jl_atexit_hook