Doc for PEP 341, needs improvement

This commit is contained in:
Neal Norwitz 2005-12-17 22:24:12 +00:00
parent 58f46b6565
commit 11ca77e6de
2 changed files with 22 additions and 20 deletions

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@ -195,26 +195,25 @@ The \keyword{try} statement specifies exception handlers and/or cleanup
code for a group of statements:
\begin{productionlist}
\production{try_stmt}
{\token{try_exc_stmt} | \token{try_fin_stmt}}
\production{try_exc_stmt}
\production{try_stmt} {try1_stmt | try2_stmt}
\production{try1_stmt}
{"try" ":" \token{suite}}
\productioncont{("except" [\token{expression}
["," \token{target}]] ":" \token{suite})+}
\productioncont{["else" ":" \token{suite}]}
\production{try_fin_stmt}
{"try" ":" \token{suite}
"finally" ":" \token{suite}}
\productioncont{["finally" ":" \token{suite}]}
\production{try2_stmt}
{"try" ":" \token{suite}}
\productioncont{"finally" ":" \token{suite}}
\end{productionlist}
There are two forms of \keyword{try} statement:
\keyword{try}...\keyword{except} and
\keyword{try}...\keyword{finally}. These forms cannot be mixed (but
they can be nested in each other).
\versionchanged[In previous versions of Python,
\keyword{try}...\keyword{except}...\keyword{finally} did not work.
\keyword{try}...\keyword{except} had to be nested in
\keyword{try}...\keyword{finally}]{2.5}
The \keyword{try}...\keyword{except} form specifies one or more
exception handlers
(the \keyword{except} clauses). When no exception occurs in the
The \keyword{except} clause(s) specify one or more exception handlers.
When no exception occurs in the
\keyword{try} clause, no exception handler is executed. When an
exception occurs in the \keyword{try} suite, a search for an exception
handler is started. This search inspects the except clauses in turn until
@ -232,6 +231,8 @@ string object, not just a string with the same value).
If no except clause matches the exception, the search for an exception
handler continues in the surrounding code and on the invocation stack.
\footnote{The exception is propogated to the invocation stack only if
there is no \keyword{finally} clause that negates the exception.}
If the evaluation of an expression in the header of an except clause
raises an exception, the original search for a handler is canceled
@ -277,12 +278,13 @@ preceding \keyword{except} clauses.
\stindex{break}
\stindex{continue}
The \keyword{try}...\keyword{finally} form specifies a `cleanup' handler. The
\keyword{try} clause is executed. When no exception occurs, the
\keyword{finally} clause is executed. When an exception occurs in the
\keyword{try} clause, the exception is temporarily saved, the
\keyword{finally} clause is executed, and then the saved exception is
re-raised. If the \keyword{finally} clause raises another exception or
If \keyword{finally} is present, it specifies a `cleanup' handler. The
\keyword{try} clause is executed, including any \keyword{except} and
\keyword{else} clauses. If an exception occurs in any of the clauses
and is not handled, the exception is temporarily saved. The
\keyword{finally} clause is executed. If there is a saved exception,
it is re-raised at the end of the \keyword{finally} clause.
If the \keyword{finally} clause raises another exception or
executes a \keyword{return} or \keyword{break} statement, the saved
exception is lost. A \keyword{continue} statement is illegal in the
\keyword{finally} clause. (The reason is a problem with the current

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@ -14,7 +14,7 @@ Core and builtins
- Implementation of PEP 341 - Unification of try/except and try/finally.
"except" clauses can now be written together with a "finally" clause in
one try statement instead of two nested ones.
one try statement instead of two nested ones. Patch #1355913.
- Bug #1379994: Builtin unicode_escape and raw_unicode_escape codec
now encodes backslash correctly.