René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Assertion failure in Modules/_io/textio.c `_io_TextIOWrapper_tell_impl: Assertion 'skip_back \u003c= PyBytes_GET_SIZE(next_input)' failed`","articleBody":"# Bug report\n\n### Bug description:\n\n```python\nimport io\nimport os\nfrom test.support import os_helper\n\nDATA_TEMPLATE = ['line1=1']\nDATA_CR = r'\\n\\r\\t'.join(DATA_TEMPLATE) + '\\r'\n\nopen_func = io.open\n\nREADMODE = 'r'\nWRITEMODE = 'wb'\n\ndata = DATA_CR\nif 'b' in WRITEMODE:\n    data = data.encode('ascii')\n\nwith open_func(os_helper.TESTFN, WRITEMODE) as fp:\n    fp.write(data)\n\nwith open_func(os_helper.TESTFN, READMODE) as fp:\n    _ = fp.readline()\n    pos = fp.tell()\n```\n\n```\npython: ../Modules/_io/textio.c:2848: _io_TextIOWrapper_tell_impl: Assertion `skip_back \u003c= PyBytes_GET_SIZE(next_input)' failed.\nAborted (core dumped)\n```\n\n\n### CPython versions tested on:\n\nCPython main branch\n\n### Operating systems tested on:\n\nLinux\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-141331\n* gh-141452\n* gh-141453\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/YuanchengJiang","@type":"Person","name":"YuanchengJiang"},"datePublished":"2025-11-09T18:34:47.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/141314/cpython/issues/141314"}