[issue19332] Guard against changing dict during iteration
Serhiy Storchaka
report at bugs.python.org
Mon Oct 21 16:02:54 CEST 2013
New submission from Serhiy Storchaka:
Currently dict iterating is guarded against changing dict's size. However when dict changed during iteration so that it's size left unchanged, this modification left unnoticed.
>>> d = dict.fromkeys('abcd')
>>> for i in d:
... print(i)
... d[i + 'x'] = None
... del d[i]
...
d
a
dx
dxx
ax
c
b
In general iterating over mutating dict considered logical error. It is good detect it as early as possible.
The proposed patch introduces a counter which changed every time when added or removed key. If an iterator detects that this counter is changed, it raises runtime error.
----------
components: Interpreter Core
files: dict_mutating_iteration.patch
keywords: patch
messages: 200784
nosy: pitrou, rhettinger, serhiy.storchaka
priority: normal
severity: normal
stage: patch review
status: open
title: Guard against changing dict during iteration
type: enhancement
versions: Python 3.4
Added file: http://bugs.python.org/file32279/dict_mutating_iteration.patch
_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue19332>
_______________________________________
More information about the Python-bugs-list
mailing list