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Update information about __del__() & reference cycles for CPython.

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This partially fixes SF bug #492619.

Fix a typo & use the new notice environment instead of (ab)using the \note
and \warning macros.
This commit is contained in:
Fred Drake 2001-12-14 22:52:41 +00:00
parent 84937719a9
commit 591dd8f620
1 changed files with 17 additions and 6 deletions
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23
Doc/ref/ref3.tex
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@ -925,7 +925,8 @@ reference is deleted. It is not guaranteed that
the interpreter exits.
\stindex{del}
\strong{Programmer's note:} \samp{del x} doesn't directly call
\begin{notice}
\samp{del x} doesn't directly call
\code{x.__del__()} --- the former decrements the reference count for
\code{x} by one, and the latter is only called when its reference
count reaches zero. Some common situations that may prevent the
@ -938,13 +939,22 @@ alive); or a reference to the object on the stack frame that raised an
unhandled exception in interactive mode (the traceback stored in
\code{sys.last_traceback} keeps the stack frame alive). The first
situation can only be remedied by explicitly breaking the cycles; the
latter two situations can be resolved by storing None in
\code{sys.exc_traceback} or \code{sys.last_traceback}.
latter two situations can be resolved by storing \code{None} in
\code{sys.exc_traceback} or \code{sys.last_traceback}. Circular
references which are garbage are detected when the option cycle
detector is enabled (it's on by default), but can only be cleaned up
if there are no Python-level \method{__del__()} methods involved.
Refer to the documentation for the \ulink{\module{gc}
module}{../lib/module-gc.html} for more information about how
\method{__del__()} methods are handled by the cycle detector,
particularly the description of the \code{garbage} value.
\end{notice}
\warning{Due to the precarious circumstances under which
\begin{notice}[warning]
Due to the precarious circumstances under which
\method{__del__()} methods are invoked, exceptions that occur during their
execution are ignored, and a warning is printed to \code{sys.stderr}
instead. Also, when \method{__del__()} is invoked is response to a module
instead. Also, when \method{__del__()} is invoked in response to a module
being deleted (e.g., when execution of the program is done), other
globals referenced by the \method{__del__()} method may already have been
deleted. For this reason, \method{__del__()} methods should do the
@ -953,7 +963,8 @@ guarantees that globals whose name begins with a single underscore are
deleted from their module before other globals are deleted; if no
other references to such globals exist, this may help in assuring that
imported modules are still available at the time when the
\method{__del__()} method is called.}
\method{__del__()} method is called.
\end{notice}
\end{methoddesc}
\begin{methoddesc}[object]{__repr__}{self}