REPL throws when `sys.ps1` is not a string · Issue #158827 · python/cpython · GitHub

Bug report

When users assign non-string values to sys.ps1 or sys.ps2, the PyREPL interactive console passes those values directly to the prompt-rendering code, which expects string values, causing repeatedly raised exceptions.

Converting both prompt values to string before use matches the expected behavior and prevents the exception loop.

Tools like the Python extension for VS Code have, for several versions, assigned a custom object with a __str__ method to sys.ps1 to handle the terminal integration logic.

Reproduction

Assign a custom object with a __str__ method to sys.ps1

>>> import sys
>>> class CustomPrompt:
...     def __init__(self, value):
...         self.value = value
...     def __str__(self):
...         return self.value
...
>>> customPS1 = CustomPrompt(":-) ")
>>> str(customPS1)
':-) '
>>> sys.ps1 = customPS1

Expected behavior is to see ':-) ' as the prompt, but the current behavior is showing a loop of exceptions.

CPython versions tested on:

3.15

Operating systems tested on:

macOS

Linked PRs

gh-130698: Convert sys.ps1 and sys.ps2 to strings before PyREPL use #158828

#130698

#130698

I think this is a different issue (although complementary). The other issue refers to catching the exceptions when trying to convert to string (example uses 1/0) while this one refers to the REPL not attempting to convert to string values first @sergey-miryanov

It seems like both issues have the same solution. You could link your PR to #130698 instead, though.

Yeah just noticed that. It also seems like both PRs are mostly similar, but yours is missing adding str(sys.ps1) to simple_interact, let me know if you prefer to add it or I can reopen my PR linked to the existing issue :)

Feel free to reopen your own PR.

REPL throws when `sys.ps1` is not a string · Issue #158827 · python/cpython · GitHub

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REPL throws when sys.ps1 is not a string #158827

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REPL throws when `sys.ps1` is not a string · Issue #158827 · python/cpython · GitHub

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REPL throws when sys.ps1 is not a string #158827

Description

Bug report

Reproduction

CPython versions tested on:

Operating systems tested on:

Linked PRs

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sergey-miryanov commented on Oct 5, 2026

edvilme commented on Oct 5, 2026

sergey-miryanov commented on Oct 5, 2026

edvilme commented on Oct 5, 2026

sergey-miryanov commented on Oct 5, 2026

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