René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"bz2.BZ2File / gzip.GZipFile / lzma.LZMAFile expose misleading `fileno` method.","articleBody":"The various compressing/decompressing file wrappers (`bz2.BZ2File`, `gzip.GZipFile`, `lzma.LZMAFile`) currently have `fileno` methods that return the _underlying_ file descriptor: https://github.com/python/cpython/blob/0a4c82ddd34a3578684b45b76f49cd289a08740b/Lib/bz2.py#L126-L129\r\n\r\nI imagine this was done because it seemed useful, but I'm not sure what use it is. You can't safely use things like `select` since the compression/decompression might buffer, and passing it to things that use the file descriptor directly will produce garbage (when reading) or corrupt the file (when writing).\r\n\r\nAn example how misleading this can be, courtesy of @ericfrederich:\r\n```\r\n\u003e\u003e\u003e import bz2\r\n\u003e\u003e\u003e import subprocess\r\n\u003e\u003e\u003e with bz2.open('/tmp/out.bz2', 'w') as f:\r\n...   subprocess.check_call(['echo', '-n', \"Why doesn't this work?\"], stdout=f)\r\n...\r\n0\r\n\u003e\u003e\u003e bz2.open('/tmp/out.bz2', 'r').read()\r\nTraceback (most recent call last):\r\n  File \"\u003cstdin\u003e\", line 1, in \u003cmodule\u003e\r\n  File \"/usr/lib/python3.7/bz2.py\", line 178, in read\r\n    return self._buffer.read(size)\r\n  File \"/usr/lib/python3.7/_compression.py\", line 103, in read\r\n    data = self._decompressor.decompress(rawblock, size)\r\nOSError: Invalid data stream\r\n\u003e\u003e\u003e open('/tmp/out.bz2', 'rb').read()\r\nb\"Why doesn't this work?BZh9\\x17rE8P\\x90\\x00\\x00\\x00\\x00\"\r\n```\r\n\r\nNote the (empty) bz2 data after the data written by the subprocess.\r\n\r\nAm I missing a situation where this is actually useful? If there isn't one, can we consider adding a warning for the confusing behaviour?","author":{"url":"https://github.com/Yhg1s","@type":"Person","name":"Yhg1s"},"datePublished":"2022-12-06T22:25:33.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/100066/cpython/issues/100066"}