Explicitly mention that people should not depend on finalization of
objects to happen immediately.
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index ddffbb3..41f6a77 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -66,6 +66,8 @@
containing circular references. See the documentation of the :mod:`gc`
module for information on controlling the collection of cyclic garbage.
Other implementations act differently and CPython may change.
+ Do not depend on immediate finalization of objects when they become
+ unreachable (ex: always close files).
Note that the use of the implementation's tracing or debugging facilities may
keep objects alive that would normally be collectable. Also note that catching