René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Suggestion: Add small clarification on Chapter 22, Example 22-5. explore1.py","articleBody":"Hi!\r\n\r\nI was going through script [explore1.py](https://github.com/fluentpython/example-code-2e/blob/master/22-dyn-attr-prop/oscon/explore1.py) from chapter 22, in particular in the [__init__ method](https://github.com/fluentpython/example-code-2e/blob/master/22-dyn-attr-prop/oscon/explore1.py#L56) and I wrote the following code instead of the code in the script:\r\n\r\n```\r\nself.__data = dict(mapping)\r\nfor key, val in self.__data.items():\r\n    if keyword.iskeyword(key):\r\n        newkey = key + '_'\r\n        self[newkey] = val\r\n        self.__data.pop(key)\r\n```\r\n\r\nOf course the above code raised the following exception:\r\n\r\n```\r\nRuntimeError: dictionary keys changed during iteration\r\n```\r\n\r\nWhich googling a bit lead me to the conclusion that modifying containers while looping is something that never should be done and I should use a shallow copy instead if necessary :)\r\n\r\nI'm creating this issue as a suggestion for perhaps a small warning/caution for a future edition. Doing a [quick search in stackoverflow](https://stackoverflow.com/search?q=RuntimeError%3A+dictionary+keys+changed+during+iteration) of the above issue showed me that this is something recurrent, even Alex Martelli did a comment about this 14 years ago [here](https://stackoverflow.com/questions/2315520/in-python-how-do-i-loop-through-the-dictionary-and-change-the-value-if-it-equal/2315529#2315529). Perhaps we can avoid some future Python programmers to stumble across this issue by warning them! 😃 \r\n\r\nBtw, thank you very much for the outstanding book! Looking forward for that next edition 😄 \r\n\r\nBest, \r\n\r\nAndy","author":{"url":"https://github.com/andyLaurito92","@type":"Person","name":"andyLaurito92"},"datePublished":"2024-10-31T00:42:53.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/48/example-code-2e/issues/48"}