ValueError: Bad Args PS1 object – when using VSCode Python extension v2024.0.0 or newer

Within the terminal panel of VSCode with Python extension enabled:

>>> python -m pip show bpython curtsies
Name: bpython
Version: 0.21
Summary: Fancy Interface to the Python Interpreter
Requires: curtsies, cwcwidth, greenlet, pygments, pyxdg, requests
Required-by: 
---
Name: curtsies
Version: 0.4.0
Summary: Curses-like terminal wrapper, with colored strings!
Requires: blessed, cwcwidth
Required-by: bpython

>>> bpython
bpython version 0.21 on top of Python 3.12.3 /root/.venvs/p312/bin/python3

Traceback (most recent call last):
  File "/root/.venvs/p312/bin/bpython", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/root/.venvs/p312/lib/python3.12/site-packages/bpython/curtsies.py", line 201, in main
    exit_value = repl.mainloop(True, paste)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/.venvs/p312/lib/python3.12/site-packages/bpython/curtsies.py", line 113, in mainloop
    self.process_event_and_paint(None)
  File "/root/.venvs/p312/lib/python3.12/site-packages/bpython/curtsies.py", line 95, in process_event_and_paint
    array, cursor_pos = self.paint()
                        ^^^^^^^^^^^^
  File "/root/.venvs/p312/lib/python3.12/site-packages/bpython/curtsiesfrontend/repl.py", line 1468, in paint
    min_height, width, self.current_cursor_line
                       ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/.venvs/p312/lib/python3.12/site-packages/bpython/curtsiesfrontend/repl.py", line 1374, in current_cursor_line
    return self.current_cursor_line_without_suggestion + suggest(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/.venvs/p312/lib/python3.12/site-packages/bpython/curtsiesfrontend/repl.py", line 1363, in current_cursor_line_without_suggestion
    "" if self.coderunner.running else self.display_line_with_prompt
                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/.venvs/p312/lib/python3.12/site-packages/bpython/curtsiesfrontend/repl.py", line 1352, in display_line_with_prompt
    prompt(self.ps1) if self.done else more(self.ps2)
    ^^^^^^^^^^^^^^^^
  File "/root/.venvs/p312/lib/python3.12/site-packages/curtsies/formatstring.py", line 883, in fmtstr
    raise ValueError(
ValueError: Bad Args: <__main__.PS1 object at 0x76bb09ea1550> (of type <class '__main__.PS1'>), (), {'fg': 36, 'bold': False}

Just ran into this same issue using Python 3.13.7 and bpython 0.25.

I am unable to reproduce the issue. Do you set PS1 to some specific value?

A similar problem occurs when running bpython in VSCode.

bpython version 0.25 on top of Python 3.13.7 /home/q/.local/share/pipx/venvs/bpython/bin/python

Traceback (most recent call last):
  File "/home/q/.local/bin/bpython", line 8, in <module>
    sys.exit(main())
             ~~~~^^
  File "/home/q/.local/share/pipx/venvs/bpython/lib/python3.13/site-packages/bpython/curtsies.py", line 245, in main
    repl.mainloop(True, paste)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/home/q/.local/share/pipx/venvs/bpython/lib/python3.13/site-packages/bpython/curtsies.py", line 170, in mainloop
    self.process_event_and_paint(None)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/home/q/.local/share/pipx/venvs/bpython/lib/python3.13/site-packages/bpython/curtsies.py", line 148, in process_event_and_paint
    array, cursor_pos = self.paint()
                        ~~~~~~~~~~^^
  File "/home/q/.local/share/pipx/venvs/bpython/lib/python3.13/site-packages/bpython/curtsiesfrontend/repl.py", line 1611, in paint
    min_height, width, self.current_cursor_line
                       ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/q/.local/share/pipx/venvs/bpython/lib/python3.13/site-packages/bpython/curtsiesfrontend/repl.py", line 1517, in current_cursor_line
    return self.current_cursor_line_without_suggestion + suggest(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/q/.local/share/pipx/venvs/bpython/lib/python3.13/site-packages/bpython/curtsiesfrontend/repl.py", line 1506, in current_cursor_line_without_suggestion
    "" if self.coderunner.running else self.display_line_with_prompt
                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/q/.local/share/pipx/venvs/bpython/lib/python3.13/site-packages/bpython/curtsiesfrontend/repl.py", line 1495, in display_line_with_prompt
    prompt(self.ps1) if self.done else more(self.ps2)
    ~~~~~~^^^^^^^^^^
  File "/home/q/.local/share/pipx/venvs/bpython/lib/python3.13/site-packages/curtsies/formatstring.py", line 868, in fmtstr
    raise ValueError(
        f"Bad Args: {string!r} (of type {type(string)}), {args!r}, {kwargs!r}"
    )
ValueError: Bad Args: <__main__.PS1 object at 0x7f6297e402f0> (of type <class '__main__.PS1'>), (), {'fg': 36, 'bold': False}

In the kitty terminal, the startup is successful:

~ ᐅ bpython
bpython version 0.25 on top of Python 3.13.7 /home/q/.local/share/pipx/venvs/bpython/bin/python
>>>

I think it's something relating to VSCode. I've gotten the error in VSCode's integrated terminal on two different computers (one Linux, one Mac) but not in any other terminal emulator. And in VSCode I get the same error regardless of the shell environment. Even happened in a bash --noprofile --norc session:

bash-5.3$ uv run --with bpython bpython
bpython version 0.25 on top of Python 3.13.7 /home/emberquill/.cache/uv/builds-v0/.tmpwSeVZH/bin/python

Traceback (most recent call last):
  File "/home/emberquill/.cache/uv/builds-v0/.tmpwSeVZH/bin/bpython", line 10, in <module>
    sys.exit(main())
             ~~~~^^
  File "/home/emberquill/.cache/uv/archive-v0/0r178DEbVx0TTGhkxMmvD/lib/python3.13/site-packages/bpython/curtsies.py", line 245, in main
    repl.mainloop(True, paste)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/home/emberquill/.cache/uv/archive-v0/0r178DEbVx0TTGhkxMmvD/lib/python3.13/site-packages/bpython/curtsies.py", line 170, in mainloop
    self.process_event_and_paint(None)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/home/emberquill/.cache/uv/archive-v0/0r178DEbVx0TTGhkxMmvD/lib/python3.13/site-packages/bpython/curtsies.py", line 148, in process_event_and_paint
    array, cursor_pos = self.paint()
                        ~~~~~~~~~~^^
  File "/home/emberquill/.cache/uv/archive-v0/0r178DEbVx0TTGhkxMmvD/lib/python3.13/site-packages/bpython/curtsiesfrontend/repl.py", line 1611, in paint
    min_height, width, self.current_cursor_line
                       ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/emberquill/.cache/uv/archive-v0/0r178DEbVx0TTGhkxMmvD/lib/python3.13/site-packages/bpython/curtsiesfrontend/repl.py", line 1517, in current_cursor_line
    return self.current_cursor_line_without_suggestion + suggest(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/emberquill/.cache/uv/archive-v0/0r178DEbVx0TTGhkxMmvD/lib/python3.13/site-packages/bpython/curtsiesfrontend/repl.py", line 1506, in current_cursor_line_without_suggestion
    "" if self.coderunner.running else self.display_line_with_prompt
                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/emberquill/.cache/uv/archive-v0/0r178DEbVx0TTGhkxMmvD/lib/python3.13/site-packages/bpython/curtsiesfrontend/repl.py", line 1495, in display_line_with_prompt
    prompt(self.ps1) if self.done else more(self.ps2)
    ~~~~~~^^^^^^^^^^
  File "/home/emberquill/.cache/uv/archive-v0/0r178DEbVx0TTGhkxMmvD/lib/python3.13/site-packages/curtsies/formatstring.py", line 868, in fmtstr
    raise ValueError(
        f"Bad Args: {string!r} (of type {type(string)}), {args!r}, {kwargs!r}"
    )
ValueError: Bad Args: <__main__.PS1 object at 0x7ff768e1c1a0> (of type <class '__main__.PS1'>), (), {'fg': 36, 'bold': False}

Actually, it only happens with the Microsoft Python extension in VSCode. It does something weird to sys.ps1:

Regular terminal:

>>> sys.ps1
'>>> '
>>> type(sys.ps1)
<class 'str'>

VSCode terminal with Python extension:

>>> sys.ps1
<__main__.PS1 object at 0x7fe2b901d400>
>>> type(sys.ps1)
<class '__main__.PS1'>
>>> str(sys.ps1)
'\x1b]633;C\x07\x1b]633;E;str(sys.ps1)\x07\x1b]633;D;0\x07\x1b]633;A\x07>>> \x1b]633;B\x07'

Edit: looks like the extension changes the PYTHONSTARTUP environment variable to point at its own pythonrc.py that changes sys.ps1 here.

@emberquill

@emberquill You are complete right! I am no longer using terminal in standalone mode, only through VSCode, and did not realize that VSCode is doing something weird with it... So the issue was not in upgrading Python but rather the version of the VSCode Python extension.

Ref https://github.com/microsoft/vscode-python/releases/tag/v2024.0.0 and microsoft/vscode-python@1ea53e2

Convert sys.ps1 to a string to work-around non-str sys.ps1 from vscode (

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ValueError: Bad Args PS1 object – when using VSCode Python extension v2024.0.0 or newer #1041

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ValueError: Bad Args PS1 object – when using VSCode Python extension v2024.0.0 or newer #1041

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chet-manley commented on Sep 18, 2025

sebastinas commented on Sep 20, 2025

paranoik1 commented on Sep 23, 2025

emberquill commented on Sep 23, 2025

emberquill commented on Sep 23, 2025

interDist commented on Sep 24, 2025

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