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Commit c2ac662

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pablogsalpablogsal
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gh-131831: Implement PEP 758 – Allow except and except* expressions without parentheses (#131833)
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‎Doc/reference/compound_stmts.rst

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+4-1Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -232,6 +232,8 @@ Additional information on exceptions can be found in section :ref:`exceptions`,
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and information on using the :keyword:`raise` statement to generate exceptions
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may be found in section :ref:`raise`.
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.. versionchanged:: next
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Support for optionally dropping grouping parentheses when using multiple exception types. See :pep:`758`.
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.. _except:
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@@ -247,7 +249,8 @@ An expression-less :keyword:`!except` clause, if present, must be last;
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it matches any exception.
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For an :keyword:`!except` clause with an expression, the
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expression must evaluate to an exception type or a tuple of exception types.
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expression must evaluate to an exception type or a tuple of exception types. Parentheses
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can be dropped if multiple exception types are provided and the ``as`` clause is not used.
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The raised exception matches an :keyword:`!except` clause whose expression evaluates
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to the class or a :term:`non-virtual base class <abstract base class>` of the exception object,
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or to a tuple that contains such a class.

‎Doc/whatsnew/3.14.rst

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+27Lines changed: 27 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -90,6 +90,33 @@ If you encounter :exc:`NameError`\s or pickling errors coming out of
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New features
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============
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.. _whatsnew314-pep758:
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PEP 758 – Allow except and except* expressions without parentheses
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------------------------------------------------------------------
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The :keyword:`except` and :keyword:`except* <except_star>` expressions now allow
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parentheses to be omitted when there are multiple exception types and the ``as`` clause is not used.
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For example the following expressions are now valid:
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.. code-block:: python
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try:
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release_new_sleep_token_album()
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except AlbumNotFound, SongsTooGoodToBeReleased:
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print("Sorry, no new album this year.")
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# The same applies to except* (for exception groups):
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try:
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release_new_sleep_token_album()
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except* AlbumNotFound, SongsTooGoodToBeReleased:
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print("Sorry, no new album this year.")
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Check :pep:`758` for more details.
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(Contributed by Pablo Galindo and Brett Cannon in :gh:`131831`.)
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.. _whatsnew314-pep649:
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PEP 649: deferred evaluation of annotations

‎Grammar/python.gram

Copy file name to clipboardExpand all lines: Grammar/python.gram
+12-8Lines changed: 12 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -435,14 +435,18 @@ try_stmt[stmt_ty]:
435435

436436
except_block[excepthandler_ty]:
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| invalid_except_stmt_indent
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| 'except' e=expression t=['as' z=NAME { z }] ':' b=block {
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_PyAST_ExceptHandler(e, (t) ? ((expr_ty) t)->v.Name.id : NULL, b, EXTRA) }
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| 'except' e=expressions ':' b=block {
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_PyAST_ExceptHandler(e, NULL, b, EXTRA) }
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| 'except' e=expression 'as' t=NAME ':' b=block {
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_PyAST_ExceptHandler(e, ((expr_ty) t)->v.Name.id, b, EXTRA) }
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| 'except' ':' b=block { _PyAST_ExceptHandler(NULL, NULL, b, EXTRA) }
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| invalid_except_stmt
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except_star_block[excepthandler_ty]:
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| invalid_except_star_stmt_indent
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| 'except' '*' e=expression t=['as' z=NAME { z }] ':' b=block {
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_PyAST_ExceptHandler(e, (t) ? ((expr_ty) t)->v.Name.id : NULL, b, EXTRA) }
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| 'except' '*' e=expressions ':' b=block {
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_PyAST_ExceptHandler(e, NULL, b, EXTRA) }
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| 'except' '*' e=expression 'as' t=NAME ':' b=block {
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_PyAST_ExceptHandler(e, ((expr_ty) t)->v.Name.id, b, EXTRA) }
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| invalid_except_star_stmt
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finally_block[asdl_stmt_seq*]:
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| invalid_finally_stmt
@@ -1356,16 +1360,16 @@ invalid_try_stmt:
13561360
| 'try' ':' block* except_star_block+ a='except' [expression ['as' NAME]] ':' {
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RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "cannot have both 'except' and 'except*' on the same 'try'") }
13581362
invalid_except_stmt:
1359-
| 'except' a=expression ',' expressions ['as' NAME ] ':' {
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RAISE_SYNTAX_ERROR_STARTING_FROM(a, "multiple exception types must be parenthesized") }
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| 'except' a=expression ',' expressions 'as' NAME ':' {
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RAISE_SYNTAX_ERROR_STARTING_FROM(a, "multiple exception types must be parenthesized when using 'as'") }
13611365
| a='except' expression ['as' NAME ] NEWLINE { RAISE_SYNTAX_ERROR("expected ':'") }
13621366
| a='except' NEWLINE { RAISE_SYNTAX_ERROR("expected ':'") }
13631367
| 'except' expression 'as' a=expression {
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RAISE_SYNTAX_ERROR_KNOWN_LOCATION(
13651369
a, "cannot use except statement with %s", _PyPegen_get_expr_name(a)) }
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invalid_except_star_stmt:
1367-
| 'except' '*' a=expression ',' expressions ['as' NAME ] ':' {
1368-
RAISE_SYNTAX_ERROR_STARTING_FROM(a, "multiple exception types must be parenthesized") }
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| 'except' '*' a=expression ',' expressions 'as' NAME ':' {
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RAISE_SYNTAX_ERROR_STARTING_FROM(a, "multiple exception types must be parenthesized when using 'as'") }
13691373
| a='except' '*' expression ['as' NAME ] NEWLINE { RAISE_SYNTAX_ERROR("expected ':'") }
13701374
| a='except' '*' (NEWLINE | ':') { RAISE_SYNTAX_ERROR("expected one or more exception types") }
13711375
| 'except' '*' expression 'as' a=expression {

‎Lib/test/test_grammar.py

Copy file name to clipboardExpand all lines: Lib/test/test_grammar.py
+4Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1375,6 +1375,8 @@ def test_try(self):
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try: 1/0
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except (EOFError, TypeError, ZeroDivisionError): pass
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try: 1/0
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except EOFError, TypeError, ZeroDivisionError: pass
1379+
try: 1/0
13781380
except (EOFError, TypeError, ZeroDivisionError) as msg: pass
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try: pass
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finally: pass
@@ -1398,6 +1400,8 @@ def test_try_star(self):
13981400
try: 1/0
13991401
except* (EOFError, TypeError, ZeroDivisionError): pass
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try: 1/0
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except* EOFError, TypeError, ZeroDivisionError: pass
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try: 1/0
14011405
except* (EOFError, TypeError, ZeroDivisionError) as msg: pass
14021406
try: pass
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finally: pass

‎Lib/test/test_syntax.py

Copy file name to clipboardExpand all lines: Lib/test/test_syntax.py
+5-33Lines changed: 5 additions & 33 deletions
Original file line numberDiff line numberDiff line change
@@ -1667,28 +1667,14 @@
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SyntaxError: invalid syntax
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Check that an multiple exception types with missing parentheses
1670-
raise a custom exception
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>>> try:
1673-
... pass
1674-
... except A, B:
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... pass
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Traceback (most recent call last):
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SyntaxError: multiple exception types must be parenthesized
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>>> try:
1680-
... pass
1681-
... except A, B, C:
1682-
... pass
1683-
Traceback (most recent call last):
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SyntaxError: multiple exception types must be parenthesized
1670+
raise a custom exception only when using 'as'
16851671
16861672
>>> try:
16871673
... pass
16881674
... except A, B, C as blech:
16891675
... pass
16901676
Traceback (most recent call last):
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SyntaxError: multiple exception types must be parenthesized
1677+
SyntaxError: multiple exception types must be parenthesized when using 'as'
16921678
16931679
>>> try:
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... pass
@@ -1697,29 +1683,15 @@
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... finally:
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... pass
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Traceback (most recent call last):
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SyntaxError: multiple exception types must be parenthesized
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SyntaxError: multiple exception types must be parenthesized when using 'as'
17011687
17021688
1703-
>>> try:
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... pass
1705-
... except* A, B:
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... pass
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Traceback (most recent call last):
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SyntaxError: multiple exception types must be parenthesized
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>>> try:
1711-
... pass
1712-
... except* A, B, C:
1713-
... pass
1714-
Traceback (most recent call last):
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SyntaxError: multiple exception types must be parenthesized
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17171689
>>> try:
17181690
... pass
17191691
... except* A, B, C as blech:
17201692
... pass
17211693
Traceback (most recent call last):
1722-
SyntaxError: multiple exception types must be parenthesized
1694+
SyntaxError: multiple exception types must be parenthesized when using 'as'
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17241696
>>> try:
17251697
... pass
@@ -1728,7 +1700,7 @@
17281700
... finally:
17291701
... pass
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Traceback (most recent call last):
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SyntaxError: multiple exception types must be parenthesized
1703+
SyntaxError: multiple exception types must be parenthesized when using 'as'
17321704
17331705
Custom exception for 'except*' without an exception type
17341706

‎Misc/NEWS.d/next/Core_and_Builtins/2025-03-28-18-59-24.gh-issue-131833.v4WvWT.rst

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+2Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,2 @@
1+
Add support for optionally dropping grouping parentheses when using multiple
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exception types as per :pep:`758`. Patch by Pablo Galindo

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