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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Bpython breaks when printing large data structures","articleBody":"I'm surprised I haven't found another issue raised about this, or maybe I missed it.\n\nThis is a frequent problem for me. If I am in the `bpython` shell and try to print out a large data structure, the shell crashes and it is frustrating. The big selling point of entering the shell is to be interactive with the environment, which means sometimes I want to display my data.\n\nIn this specific instance, I have a nested list structure. that looks like this\n\n```\n[\n  [\"string\",\"string\",\"string\"..],\n  [\"string\",\"string\",\"string\"..],\n  ...\n]\n```\n\nWhen I do a bit of debugging\n```python\nsum([len(y) for x in my_nested_list[:50] for y in x])\n```\nI get `36453`. So this means the excerpt I'm going to \"print\" to my screen has 36,453 bytes of characters in it, spread across 30 nested lists.\n\nIn `bpython` shell, when I simply do\n```\n\u003e\u003e\u003e my_nested_list[:50]\n```\nThe shell crashes:\n```\nTraceback (most recent call last):\n  File \"/path/to/venv/bin/bpython\", line 8, in \u003cmodule\u003e\n    sys.exit(main())\n             ~~~~^^\n  File \"/path/to/venv/lib64/python3.13/site-packages/bpython/curtsies.py\", line 245, in main\n    repl.mainloop(True, paste)\n    ~~~~~~~~~~~~~^^^^^^^^^^^^^\n  File \"/path/to/venv/lib64/python3.13/site-packages/bpython/curtsies.py\", line 178, in mainloop\n    self.process_event_and_paint(e)\n    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^\n  File \"/path/to/venv/lib64/python3.13/site-packages/bpython/curtsies.py\", line 149, in process_event_and_paint\n    scrolled = self.window.render_to_terminal(array, cursor_pos)\n  File \"/path/to/venv/lib64/python3.13/site-packages/curtsies/window.py\", line 491, in render_to_terminal\n    self.scroll_down()\n    ~~~~~~~~~~~~~~~~^^\n  File \"/path/to/venv/lib64/python3.13/site-packages/curtsies/window.py\", line 56, in scroll_down\n    with self.t.location(x=0, y=1000000):\n         ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^\n  File \"/usr/lib64/python3.13/contextlib.py\", line 141, in __enter__\n    return next(self.gen)\n  File \"/path/to/venv/lib64/python3.13/site-packages/blessed/terminal.py\", line 594, in location\n    self.stream.flush()\n    ~~~~~~~~~~~~~~~~~^^\n  File \"/path/to/venv/lib64/python3.13/site-packages/bpython/curtsiesfrontend/repl.py\", line 623, in sigwinch_handler\n    cursor_dy = self.get_cursor_vertical_diff()\n  File \"/path/to/venv/lib64/python3.13/site-packages/bpython/curtsies.py\", line 118, in get_cursor_vertical_diff\n    return self.window.get_cursor_vertical_diff()\n           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^\n  File \"/path/to/venv/lib64/python3.13/site-packages/curtsies/window.py\", line 398, in get_cursor_vertical_diff\n    cursor_dy += self._get_cursor_vertical_diff_once()\n                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^\n  File \"/path/to/venv/lib64/python3.13/site-packages/curtsies/window.py\", line 406, in _get_cursor_vertical_diff_once\n    row, col = self.get_cursor_position()\n               ~~~~~~~~~~~~~~~~~~~~~~~~^^\n  File \"/path/to/venv/lib64/python3.13/site-packages/curtsies/window.py\", line 315, in get_cursor_position\n    return self.t.get_location()\n           ~~~~~~~~~~~~~~~~~~~^^\n  File \"/path/to/venv/lib64/python3.13/site-packages/blessed/terminal.py\", line 651, in get_location\n    match = self._query_response(\n        self.u7 or u'\\x1b[6n', self.caps['cursor_report'].re_compiled, timeout\n    )\n  File \"/path/to/venv/lib64/python3.13/site-packages/blessed/terminal.py\", line 528, in _query_response\n    self.stream.flush()\n    ~~~~~~~~~~~~~~~~~^^\nRuntimeError: reentrant call inside \u003c_io.BufferedWriter name='\u003cstdout\u003e'\u003e\n```","author":{"url":"https://github.com/truck-iguana","@type":"Person","name":"truck-iguana"},"datePublished":"2025-04-27T18:00:26.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/1037/bpython/issues/1037"}