René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Runtime error in Example A-2","articleBody":"I'm trying to run the `Example A-2` (page 689 in the First Edition).\r\nI'm not sure if it's something wrong that I'm doing.. but I read the code 10 times. I'm sure it is the same of the book.\r\n\r\nI'm running this code as:\r\n```\r\n$python example_a_2__generate_array.py\r\n```\r\nwhere my Python version is `3.8.5`. Then I see this error:\r\n```\r\ninitial sample: 10500000 elements\r\nTraceback (most recent call last):\r\n  File \"example_a_2__generate_array.py\", line 19, in \u003cmodule\u003e\r\n    with len(sample) \u003c SAMPLE_LEN:\r\nAttributeError: __enter__\r\n```\r\n\r\n**Some reasoning:**\r\nI'm not reasigning the `open` function (as suggested [here](https://stackoverflow.com/questions/53564755/python-error-attributeerror-enter) for one possible cause).\r\n\r\n**Possible solution:**\r\nMaybe line 19 should be replaced by:\r\n```\r\nif len(sample) \u003c SAMPLE_LEN:\r\n```\r\n\r\nI tried that and got a good looking output:\r\n```\r\ninitial sample: 10500000 elements\r\ncomplete sample: 10500000 elements\r\nnot selected: 500000 samples\r\n  writing not_selected.arr\r\nselected: 10000000 samples\r\n  writing selected.arr\r\n ```\r\n \r\n And they seem to have been created correctly:\r\n```\r\n$ls -la *selected*\r\n-rw-rw-r-- 1 lucas lucas  4000000 mai 13 14:57 not_selected.arr\r\n-rw-rw-r-- 1 lucas lucas 80000000 mai 13 14:57 selected.arr\r\n```\r\n\r\n\r\nPS.: Thank you for the book and sharing your knowledge!","author":{"url":"https://github.com/CavalcanteLucas","@type":"Person","name":"CavalcanteLucas"},"datePublished":"2021-05-13T18:55:21.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/52/example-code/issues/52"}