JSON CLI: I/O operation on closed file" when parsing JSON Lines file

Bug report

Bug description:

With any JSON Lines file, such as:

❯ cat input.jsonl
{"ingredients":["frog", "water", "chocolate", "glucose"]}
{"ingredients":["chocolate","steel bolts"]}

This works on Python 3.12:

❯ python3.12 --version
Python 3.12.10

❯ python3.12 -m json.tool --json-lines input.jsonl
{
    "ingredients": [
        "frog",
        "water",
        "chocolate",
        "glucose"
    ]
}
{
    "ingredients": [
        "chocolate",
        "steel bolts"
    ]
}

But not 3.13 or higher:

❯ python3.13 --version
Python 3.13.3

❯ python3.13 -m json.tool --json-lines input.jsonl
I/O operation on closed file.

❯ python3.14 --version
Python 3.14.0a7

❯ python3.14 -m json.tool --json-lines input.jsonl
I/O operation on closed file.

❯ ./python.exe --version --version
Python 3.14.0a7+ (heads/main:e42bda94411, Apr 17 2025, 14:59:38) [Clang 16.0.0 (clang-1600.0.26.6)]

❯ ./python.exe Lib/test/test_json/test_tool.py -h

❯ ./python.exe -m json.tool --json-lines input.jsonl
I/O operation on closed file.

CPython versions tested on:

3.13, 3.14, CPython main branch

Operating systems tested on:

macOS, Linux

Linked PRs

There's also an issue with the "in place" functionality. This is captured in a unit test, but there's no mention of this requirement or functionality in the code.

In place can overwrite the current file, but requires special attention.

python -m json.tool example.json example.json

For the in place functionality, it should probably write to a tmp file, then atomically overwrite the original file and delete the tmp file.

The use case of in place and --json-lines is a bit odd (needs --no-indent), but it still should mechanically work and not error out.

>> cat a.jline                                                
{"alpha": 123,                     "beta": 122345}
{"alpha": 124,       "beta": 456}

From a file, using --no-indent can cleanup a file.

>> python  -m json.tool --no-indent --json-lines a.jline 
{"alpha": 123, "beta": 122345}
{"alpha": 124, "beta": 456}

In place will break and overwrite the original file and leave an empty file, effectively deleting(!) the original file.

>> cat a.jline       
{"alpha": 123,                     "beta": 122345}
{"alpha": 124,       "beta": 456}
>> python -m json.tool --json-lines --no-indent a.jline a.jline
I/O operation on closed file.
>> cat a.jline 
>>

gh-132631: Fix "I/O operation on closed file" when parsing JSON Lines…

[3.14] gh-132631: Fix "I/O operation on closed file" when parsing JSO…

[3.13] gh-132631: Fix "I/O operation on closed file" when parsing JSO…

pythongh-132631: Fix "I/O operation on closed file" when parsing JSON…

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JSON CLI: I/O operation on closed file" when parsing JSON Lines file #132631

Bug report

Bug description:

CPython versions tested on:

Operating systems tested on:

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JSON CLI: I/O operation on closed file" when parsing JSON Lines file #132631

Description

Bug report

Bug description:

CPython versions tested on:

Operating systems tested on:

Linked PRs

Activity

nineteendo commented on Sep 16, 2025

mpkocher commented on Sep 16, 2025

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