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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"sys._base_executable may not exist on posix venvs made with `--copies`","articleBody":"\u003c!--\r\n  If you're new to Python and you're not sure whether what you're experiencing is a bug, the CPython issue tracker is not\r\n  the right place to seek help. Consider the following options instead:\r\n\r\n  - reading the Python tutorial: https://docs.python.org/3/tutorial/\r\n  - posting in the \"Users\" category on [discuss.python.org](http://discuss.python.org/): https://discuss.python.org/c/users/7\r\n  - emailing the Python-list mailing list: https://mail.python.org/mailman/listinfo/python-list\r\n  - searching our issue tracker (https://github.com/python/cpython/issues) to see if\r\n    your problem has already been reported\r\n--\u003e\r\n\r\n\r\n# Bug report\r\n\r\nPython `venv` on POSIX environments creates a bin directory with:\r\n- `python`\r\n- `python{VERSION_MAJOR}`\r\n- `python(VERSION_MAJOR}.{VERSION_MINOR}`\r\n\r\nWhen executing `python` out of a venv made with the `--copies` argument specified (that is, it doesn't use symlinks), the calculation of `base_executable` will blindly append the basename of the executable to the value from the `home` key from `pyvenv.cfg`, meaning base_executable = $home_dir/basename(executable)\r\n   \r\nWith recent changes made in 3.11, on Linux, the `home` key is determined by the `base_executable` of the initial python that created the venv. Even if the venv is \"nested\", `home` will still point to the topmost non-venv python bin path. \r\n\r\nHowever, this can be problematic because source installations via `make install` only provide:\r\n- `python{VERSION_MAJOR}`\r\n- `python(VERSION_MAJOR}.{VERSION_MINOR}`\r\n\r\nThis means if \"python\" is invoked from a venv, the resultant `base_executable` may be an invalid file that applications may be relying upon via `sys._base_executable` (both `venv` and `virtualenv` use this value)\r\n\r\nMost distributions do not distribute a version-less \"python\" as part of the divorce of python2 and python3 via guidance from PEP 394 (though some offer a convenience package to symlink it)\r\n\r\nA suggested fix in previous discussions was to include a field in pyvenv.cfg specifying the base executable, but that may require updates to PEP 405 since there's only two documented keys for this file and other implementations such as `virtualenv` would want to conform to new specifications (virtualenv already stores a base-executable key so there could be a conflict)\r\n\r\nIn lieu of that, a simple `stat` to check for alternatives seems reasonable without impacting startup performance overly much.\r\n\r\nSince this affects 3.11+, it'd be nice to see a fix backported to that branch.\r\n\r\nExample:\r\n\r\n```\r\nvfazio@Zephyrus:~/development/cpython$ ./configure\r\nvfazio@Zephyrus:~/development/cpython$ make -j12\r\nvfazio@Zephyrus:~/development/cpython$ DESTDIR=/tmp/tmp.w9Bqq4Aibx/ make install\r\nvfazio@Zephyrus:~/development/cpython$ cd /tmp/tmp.w9Bqq4Aibx/\r\nvfazio@Zephyrus:~/development/cpython$ /tmp/tmp.w9Bqq4Aibx/usr/local/bin/python3 -V\r\nPython 3.12.0a1+\r\nvfazio@Zephyrus:~/development/cpython$ /tmp/tmp.w9Bqq4Aibx/usr/local/bin/python3 -m venv --clear --copies /tmp/tmp.307I606AVh/\r\nvfazio@Zephyrus:~/development/cpython$ /tmp/tmp.307I606AVh/bin/python -c \"import sys; print((sys._base_executable, sys.version))\"\r\n('/tmp/tmp.w9Bqq4Aibx/usr/local/bin/python', '3.12.0a1+ (heads/vfazio-base-exec-fallback:267e1040a9, Nov  6 2022, 15:16:06) [GCC 9.4.0]')\r\nvfazio@Zephyrus:~/development/cpython$ test -e /tmp/tmp.w9Bqq4Aibx/usr/local/bin/python; echo $?\r\n1\r\nvfazio@Zephyrus:~/development/cpython$\r\n\r\n\r\nroot@fe1d04cd5d49:/tmp/tmp.SfKfnBG1SH# usr/local/bin/python3 -V\r\nPython 3.11.0\r\nroot@fe1d04cd5d49:/tmp/tmp.SfKfnBG1SH# mktemp -d\r\n/tmp/tmp.DDS5n25q4C\r\nroot@fe1d04cd5d49:/tmp/tmp.SfKfnBG1SH# usr/local/bin/python3 -m venv --copies --clear /tmp/tmp.DDS5n25q4C/\r\nroot@fe1d04cd5d49:/tmp/tmp.SfKfnBG1SH# /tmp/tmp.DDS5n25q4C/bin/python -c \"import sys; print((sys._base_executable, sys.version))\"\r\n('/tmp/tmp.SfKfnBG1SH/usr/local/bin/python', '3.11.0 (main, Nov  5 2022, 11:43:28) [GCC 10.2.1 20210110]')\r\nroot@fe1d04cd5d49:/tmp/tmp.SfKfnBG1SH# test -e /tmp/tmp.SfKfnBG1SH/usr/local/bin/python; echo $?\r\n1\r\n```\r\n\r\n\r\n# Your environment\r\n\r\n\u003c!-- Include as many relevant details as possible about the environment you experienced the bug in --\u003e\r\n\r\n- CPython versions tested on: 3.11, main (3.12.0a1+)\r\n- Operating system and architecture: Linux x86-64\r\n\r\n\u003c!--\r\nYou can freely edit this text. Remove any lines you believe are unnecessary.\r\n--\u003e\r\n\r\nrelated discussion and MRs:\r\nhttps://bugs.python.org/issue46028\r\nhttps://github.com/python/cpython/pull/29041\r\nhttps://github.com/python/cpython/pull/30144\r\n\r\nrelated issues:\r\nhttps://github.com/pypa/virtualenv/issues/2440\r\nhttps://github.com/python-poetry/poetry/issues/6940\n\n\u003c!-- gh-pr-number: gh-99206 --\u003e\n* PR: gh-99206\n\u003c!-- /gh-pr-number --\u003e\n\n\n\u003c!-- gh-pr-number: gh-99340 --\u003e\n* PR: gh-99340\n\u003c!-- /gh-pr-number --\u003e\n","author":{"url":"https://github.com/vfazio","@type":"Person","name":"vfazio"},"datePublished":"2022-11-07T15:10:59.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/99204/cpython/issues/99204"}