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Since bpo-40222 "Zero cost exception handling", code object created by from bytecode with code.replace(co_code=new_code) no longer catch exceptions on Python 3.11, unless an exception table is set explicitly.
Example:
---
def f():
 try:
 print("raise")
 raise ValueError
 except ValueError:
 print("except")
 else:
 print("else")
 print("exit func")
def g(): pass
if 1:
 code = f.__code__
 g.__code__ = g.__code__.replace(
 co_code=code.co_code,
 co_consts=code.co_consts,
 co_names=code.co_names,
 co_flags=code.co_flags,
 co_stacksize=code.co_stacksize)
else:
 g.__code__ = f.__code__ # this code path works on Python 3.11
g()
---
Output with Python 3.10 (ok):
---
raise
except
exit func
---
Output with Python 3.11 (oops):
---
raise
Traceback (most recent call last):
 ...
ValueError
---
Would it make sense to automatically compute co_exceptiontable on code.replace(co_code=new_code)? If it's computed automatically, I don't know if it makes still sense to call code.replace(co_code=new_code, co_exceptiontable=new_table).
It seems like currently, the only implementation to build an exception table lives in Python/compile.c which compiles AST to bytecode. It cannot be reused for code.replace() which takes bytecode as input, not AST.
--
If code.replace() is not updated to recompute co_exceptiontable, at least, it would be nice to document the bpo-40222 changes in What's New in Python 3.11 and in the CodeType documentation:
* https://docs.python.org/dev/library/types.html#types.CodeType
* https://docs.python.org/dev/whatsnew/3.11.html