New submission from Andreas Poehlmann <andr...@poehlmann.io>:
Hello, I encountered an issue with collections.ChainMap, that was introduced when https://bugs.python.org/issue32792 got fixed. Iterating a ChainMap will call __getitem__ on its underlying maps: >>> from collections import UserDict, ChainMap >>> class MyDict(UserDict): ... def __getitem__(self, k): ... print("expensive computation", k) ... return super().__getitem__(k) ... >>> set(ChainMap(MyDict(a=1, b=2, c=3))) expensive computation a expensive computation b expensive computation c {'c', 'b', 'a'} ---------- components: Library (Lib) messages: 381971 nosy: ap-- priority: normal severity: normal status: open title: collections.ChainMap.__iter__ calls __getitem__ on underlying maps type: behavior versions: Python 3.10, Python 3.7, Python 3.8, Python 3.9 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue42487> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
