[Python-Dev] Making sure dictionary adds/deletes during iteration always raise exception (original) (raw)

Serhiy Storchaka storchaka at gmail.com
Tue Dec 13 18:02:50 EST 2016


On 13.12.16 11:51, Max Moroz wrote:

Would it be worth ensuring that an exception is ALWAYS raised if a key is added to or deleted from a dictionary during iteration?

Currently, dict.iter only raises "RuntimeError" when "dictionary changed size during iteration". I managed to add 1 key and delete 1 key from the dictionary in the same iteration of the loop (the code was in a callback function invoked in the loop) - of course without any exception. (I hope I'm right in assuming that adding and deleting entries in the loop is unsafe whether or not number of adds equals number of deletes.) I suspect the cost of a more comprehensive error reporting is not worth the benefit, but I thought I'd ask anyway.

The patch implementing this was rejected.

http://bugs.python.org/issue19332



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