New submission from SylvainDe:
Disclaimer: This is very minor, impacts only Python 2 and is maybe not even a
bug.
Context: I was randomly changing attribute of Exception objects when I
discovered something I did not expect : sometimes when an exception occurs, a
new object is raised (which is what I expected), sometimes a previously thrown
exception is re-thrown (which surprised me).
More specifically, MemoryError objects seem to be reused while most of the
other exceptions I've played with where newly created.
One can easily see this happening in the following piece of code :
- first a NameError is caught and updated
- then, we run the same code and print the re-caught exception : it is a new
one
- then, a MemoryError is caught and updated
- then, we run the same code and print the re-caught exception : it is the
same as previously.
pre
from __future__ import print_function
old_e = None
try:
foobar
except NameError as old_e:
print(old_e:, old_e)
old_e.args = tuple(['NEW VALUE'])
print(old_e:, old_e)
try:
foobar
except NameError as new_e:
print(new_e:, new_e)
print(old_e is new_e)
old_e = None
try:
l = [0] * 99
except MemoryError as old_e:
print(old_e:, old_e)
old_e.args = tuple(['NEW VALUE'])
print(old_e:, old_e)
try:
l = [0] * 99
except MemoryError as new_e:
print(new_e:, new_e)
print(old_e is new_e)
/pre
For the record, I am quite aware that this shouldn't impact anyone using Python
normally. I was just messing around as part of a toy project where I try to
enhance exception messages for a better user experience (
https://github.com/SylvainDe/DidYouMean-Python ).
--
components: Interpreter Core
messages: 245940
nosy: SylvainDe
priority: normal
severity: normal
status: open
title: Same MemoryError object gets thrown from different places.
versions: Python 2.7
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http://bugs.python.org/issue24529
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