On Mar 20, 2017 1:26 PM, "Antoine Pitrou" email@example.com wrote:
On Mon, 20 Mar 2017 18:28:29 +0100 Oleg Nesterov firstname.lastname@example.org wrote:
I started to learn python a few days ago and I am trying to understand
__del__() actually does. https://docs.python.org/3/
object.__del__(self) ... Note that it is possible (though not recommended!) for the __del__() method to postpone destruction of the instance by creating a new reference to it. It may then be called at a later time when this new reference is deleted.
This sentence is not technically wrong, but it can easily be misleading. It says "it *may* then be called at a later time" and probably it should say "it may or may not be called at a later time, depending on the Python implementation you are using".
Modern CPython, and all extant versions of PyPy and Jython, guarantee that __del__ is called at most once. MicroPython doesn't support user-defined __del__ methods.
It's fine if the text wants to leave that open, but the current phrasing is pretty misleading IMO. I also read it as saying that __del__ would be called again if the object is collected again (which may or may not happen). But AFAICT there are actually zero implementations where this is true. Probably worth a small edit :-)