From c95f8bc2700b42f4568886505a819816c9b0ba28 Mon Sep 17 00:00:00 2001 From: Colin Watson Date: Sun, 20 Dec 2020 18:24:10 +0000 Subject: [PATCH] bpo-42669: Document that `except` rejects nested tuples (GH-23822) In Python 2, it was possible to use `except` with a nested tuple, and occasionally natural. For example, `zope.formlib.interfaces.InputErrors` is a tuple of several exception classes, and one might reasonably think to do something like this: try: self.getInputValue() return True except (InputErrors, SomethingElse): return False As of Python 3.0, this raises `TypeError: catching classes that do not inherit from BaseException is not allowed` instead: one must instead either break it up into multiple `except` clauses or flatten the tuple. However, the reference documentation was never updated to match this new restriction. Make it clear that the definition is no longer recursive. Automerge-Triggered-By: GH:ericvsmith --- Doc/reference/compound_stmts.rst | 3 ++- Misc/ACKS | 1 + 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/Doc/reference/compound_stmts.rst b/Doc/reference/compound_stmts.rst index a55aacccc16..8da74c79801 100644 --- a/Doc/reference/compound_stmts.rst +++ b/Doc/reference/compound_stmts.rst @@ -254,7 +254,8 @@ present, must be last; it matches any exception. For an except clause with an expression, that expression is evaluated, and the clause matches the exception if the resulting object is "compatible" with the exception. An object is compatible with an exception if it is the class or a base class of the exception -object or a tuple containing an item compatible with the exception. +object, or a tuple containing an item that is the class or a base class of +the exception object. If no except clause matches the exception, the search for an exception handler continues in the surrounding code and on the invocation stack. [#]_ diff --git a/Misc/ACKS b/Misc/ACKS index 381aed1009c..80e51f93e3a 100644 --- a/Misc/ACKS +++ b/Misc/ACKS @@ -1849,6 +1849,7 @@ Zachary Ware Barry Warsaw Steve Waterbury Bob Watson +Colin Watson David Watson Aaron Watters Henrik Weber