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bpo-45292: [PEP-654] add except* (pythonGH-29581)
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lines changed

‎Doc/library/ast.rst‎

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@@ -1167,6 +1167,37 @@ Control flow
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type_ignores=[])
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.. class:: TryStar(body, handlers, orelse, finalbody)
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``try`` blocks which are followed by ``except*`` clauses. The attributes are the
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same as for :class:`Try` but the :class:`ExceptHandler` nodes in ``handlers``
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are interpreted as ``except*`` blocks rather then ``except``.
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.. doctest::
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>>> print(ast.dump(ast.parse("""
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... try:
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... ...
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... except* Exception:
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... ...
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... """), indent=4))
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Module(
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body=[
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TryStar(
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body=[
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Expr(
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value=Constant(value=Ellipsis))],
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handlers=[
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ExceptHandler(
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type=Name(id='Exception', ctx=Load()),
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body=[
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Expr(
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value=Constant(value=Ellipsis))])],
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orelse=[],
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finalbody=[])],
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type_ignores=[])
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.. class:: ExceptHandler(type, name, body)
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A single ``except`` clause. ``type`` is the exception type it will match,

‎Doc/library/dis.rst‎

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@@ -872,8 +872,10 @@ All of the following opcodes use their arguments.
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.. versionadded:: 3.1
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.. opcode:: JUMP_IF_NOT_EXC_MATCH (target)
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Performs exception matching for ``except``.
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Tests whether the second value on the stack is an exception matching TOS,
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and jumps if it is not. Pops one value from the stack.
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@@ -883,6 +885,30 @@ All of the following opcodes use their arguments.
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This opcode no longer pops the active exception.
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.. opcode:: JUMP_IF_NOT_EG_MATCH (target)
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Performs exception matching for ``except*``. Applies ``split(TOS)`` on
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the exception group representing TOS1. Jumps if no match is found.
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Pops one item from the stack. If a match was found, pops the 3 items representing
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the exception and pushes the 3 items representing the non-matching part of
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the exception group, followed by the 3 items representing the matching part.
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In other words, in case of a match it pops 4 items and pushes 6.
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.. versionadded:: 3.11
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.. opcode:: PREP_RERAISE_STAR
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Combines the raised and reraised exceptions list from TOS, into an exception
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group to propagate from a try-except* block. Uses the original exception
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group from TOS1 to reconstruct the structure of reraised exceptions. Pops
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two items from the stack and pushes a triplet representing the exception to
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reraise or three ``None`` if there isn't one.
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.. versionadded:: 3.11
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.. opcode:: JUMP_IF_TRUE_OR_POP (target)
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If TOS is true, sets the bytecode counter to *target* and leaves TOS on the

‎Doc/whatsnew/3.11.rst‎

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@@ -65,6 +65,8 @@ Summary -- Release highlights
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.. PEP-sized items next.
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PEP-654: Exception Groups and ``except*``.
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(Contributed by Irit Katriel in :issue:`45292`.)
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New Features
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============

‎Grammar/python.gram‎

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@@ -403,6 +403,8 @@ try_stmt[stmt_ty]:
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| invalid_try_stmt
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| 'try' &&':' b=block f=finally_block { _PyAST_Try(b, NULL, NULL, f, EXTRA) }
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| 'try' &&':' b=block ex[asdl_excepthandler_seq*]=except_block+ el=[else_block] f=[finally_block] { _PyAST_Try(b, ex, el, f, EXTRA) }
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| 'try' &&':' b=block ex[asdl_excepthandler_seq*]=except_star_block+ el=[else_block] f=[finally_block] { _PyAST_TryStar(b, ex, el, f, EXTRA) }
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# Except statement
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# ----------------
@@ -413,6 +415,11 @@ except_block[excepthandler_ty]:
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_PyAST_ExceptHandler(e, (t) ? ((expr_ty) t)->v.Name.id : NULL, 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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| invalid_except_stmt
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finally_block[asdl_stmt_seq*]:
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| invalid_finally_stmt
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| 'finally' &&':' a=block { a }
@@ -1192,18 +1199,24 @@ invalid_try_stmt:
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| a='try' ':' NEWLINE !INDENT {
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RAISE_INDENTATION_ERROR("expected an indented block after 'try' statement on line %d", a->lineno) }
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| 'try' ':' block !('except' | 'finally') { RAISE_SYNTAX_ERROR("expected 'except' or 'finally' block") }
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| 'try' ':' block* ((except_block+ except_star_block) | (except_star_block+ except_block)) block* {
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RAISE_SYNTAX_ERROR("cannot have both 'except' and 'except*' on the same 'try'") }
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invalid_except_stmt:
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| 'except' a=expression ',' expressions ['as' NAME ] ':' {
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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") }
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| a='except' expression ['as' NAME ] NEWLINE { RAISE_SYNTAX_ERROR("expected ':'") }
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| a='except' '*'? expression ['as' NAME ] NEWLINE { RAISE_SYNTAX_ERROR("expected ':'") }
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| a='except' NEWLINE { RAISE_SYNTAX_ERROR("expected ':'") }
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| a='except' '*' (NEWLINE | ':') { RAISE_SYNTAX_ERROR("expected one or more exception types") }
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invalid_finally_stmt:
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| a='finally' ':' NEWLINE !INDENT {
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RAISE_INDENTATION_ERROR("expected an indented block after 'finally' statement on line %d", a->lineno) }
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invalid_except_stmt_indent:
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| a='except' expression ['as' NAME ] ':' NEWLINE !INDENT {
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RAISE_INDENTATION_ERROR("expected an indented block after 'except' statement on line %d", a->lineno) }
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| a='except' ':' NEWLINE !INDENT { RAISE_SYNTAX_ERROR("expected an indented block after except statement on line %d", a->lineno) }
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invalid_except_star_stmt_indent:
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| a='except' '*' expression ['as' NAME ] ':' NEWLINE !INDENT {
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RAISE_INDENTATION_ERROR("expected an indented block after 'except*' statement on line %d", a->lineno) }
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invalid_match_stmt:
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| "match" subject_expr !':' { CHECK_VERSION(void*, 10, "Pattern matching is", RAISE_SYNTAX_ERROR("expected ':'") ) }
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| a="match" subject=subject_expr ':' NEWLINE !INDENT {

‎Include/internal/pycore_ast.h‎

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‎Include/internal/pycore_ast_state.h‎

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@@ -132,6 +132,7 @@ struct ast_state {
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PyObject *Sub_singleton;
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PyObject *Sub_type;
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PyObject *Subscript_type;
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PyObject *TryStar_type;
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PyObject *Try_type;
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PyObject *Tuple_type;
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PyObject *TypeIgnore_type;

‎Include/internal/pycore_pyerrors.h‎

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@@ -92,6 +92,14 @@ PyAPI_FUNC(PyObject *) _PyErr_FormatFromCauseTstate(
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const char *format,
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...);
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PyAPI_FUNC(PyObject *) _PyExc_CreateExceptionGroup(
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const char *msg,
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PyObject *excs);
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PyAPI_FUNC(PyObject *) _PyExc_ExceptionGroupProjection(
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PyObject *left,
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PyObject *right);
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PyAPI_FUNC(int) _PyErr_CheckSignalsTstate(PyThreadState *tstate);
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PyAPI_FUNC(void) _Py_DumpExtensionModules(int fd, PyInterpreterState *interp);

‎Include/opcode.h‎

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‎Lib/ast.py‎

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@@ -683,6 +683,7 @@ def __init__(self, *, _avoid_backslashes=False):
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self._type_ignores = {}
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self._indent = 0
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self._avoid_backslashes = _avoid_backslashes
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self._in_try_star = False
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def interleave(self, inter, f, seq):
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"""Call f on each item in seq, calling inter() in between."""
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self.write(" from ")
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self.traverse(node.cause)
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def visit_Try(self, node):
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def do_visit_try(self, node):
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self.fill("try")
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with self.block():
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self.traverse(node.body)
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with self.block():
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self.traverse(node.finalbody)
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def visit_Try(self, node):
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prev_in_try_star = self._in_try_star
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try:
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self._in_try_star = False
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self.do_visit_try(node)
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finally:
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self._in_try_star = prev_in_try_star
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def visit_TryStar(self, node):
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prev_in_try_star = self._in_try_star
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try:
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self._in_try_star = True
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self.do_visit_try(node)
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finally:
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self._in_try_star = prev_in_try_star
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def visit_ExceptHandler(self, node):
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self.fill("except")
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self.fill("except*" if self._in_try_star else "except")
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if node.type:
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self.write(" ")
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self.traverse(node.type)

‎Lib/importlib/_bootstrap_external.py‎

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@@ -371,6 +371,7 @@ def _write_atomic(path, data, mode=0o666):
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# Python 3.11a3 3464 (bpo-45636: Merge numeric BINARY_*/INPLACE_* into
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# BINARY_OP)
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# Python 3.11a3 3465 (Add COPY_FREE_VARS opcode)
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# Python 3.11a3 3466 (bpo-45292: PEP-654 except*)
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#
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# MAGIC must change whenever the bytecode emitted by the compiler may no
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# Whenever MAGIC_NUMBER is changed, the ranges in the magic_values array
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# in PC/launcher.c must also be updated.
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MAGIC_NUMBER = (3465).to_bytes(2, 'little') + b'\r\n'
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MAGIC_NUMBER = (3466).to_bytes(2, 'little') + b'\r\n'
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_RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little') # For import.c
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_PYCACHE = '__pycache__'

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