PyREPL raises exception while trying to write to the history file on a read-only file system

[vladimir-poghosyan]

Bug report

Bug description:

When using new Python 3.13 pyrepl on a read-only file system, attempting to exit the REPL raises the following exception: OSError: [Errno 30] Read-only file system: '/root/.python_history'. The same setup works with Python 3.12.

dev:/home/dev$ docker run -it --read-only python:3.12-slim-bookworm python3
Python 3.12.7 (main, Nov 12 2024, 02:26:49) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> print('hello')
hello
>>> exit()
dev:/home/dev$ docker run -it --read-only python:3.13-slim-bookworm python3
Python 3.13.1 (main, Dec  4 2024, 20:40:24) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> print('hello')
hello
>>> exit()
Exception ignored in atexit callback <function register_readline.<locals>.write_history at 0x7f56689a3600>:
Traceback (most recent call last):
  File "<frozen site>", line 574, in write_history
  File "/usr/local/lib/python3.13/_pyrepl/readline.py", line 453, in write_history_file
    f = open(os.path.expanduser(filename), "w",
OSError: [Errno 30] Read-only file system: '/root/.python_history'

CPython versions tested on:

3.12, 3.13

Operating systems tested on:

Linux

Linked PRs

• gh-128066: Fixed PyREPL history saving on read-only file systems #128088
• gh-128066: Properly handle history file writes for RO fs on PyREPL #134380
• [3.14] gh-128066: Properly handle history file writes for RO fs on PyREPL (gh-134380) #134385
• [3.13] gh-128066: Properly handle history file writes for RO fs on PyREPL (gh-134380) #134386

[ZeroIntensity]

I think the easiest fix would be to catch OSErrors there, and just log a warning if something goes wrong.

[skirpichev]

It's silly that we get this error only at the end of session.

Rather than catch OSError, maybe we should map EROFS errno to PermissionError on Linux. (Call to write_history_file() is wrapped with except (FileNotFoundError, PermissionError).)

[feoh]

Fix in hand. Tested locally by stealing the official Python image build dockerfile but using my own modified tarball with the fix.

╭─cpatti at rocinante in ~/src/personal 25-05-20 - 14:18:58
╰─○ docker run -it --read-only pyrepl_tst python3                       <region:us-east-1>
zsh: correct 'python3' to 'python' [nyae]? n
Python 3.15.0a0 (heads/cpatti_issue_128066-dirty:01225ff4a74, May 20 2025, 18:17:11) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> print("Hellorld!")
Hellorld!
>>>