FileIO.readall() should raise "UnsupportedOperation" when in "w" mode

@evanWang1409

BPO	41352
Nosy	@evanWang1409
PRs	bpo-41352: Raise UnsupportedOperation for FileIO.readall() in "w" mode #21568

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-07-20.21:14:00.553>
labels = ['type-bug', '3.9', 'expert-IO', '3.11', 'library', '3.10']
title = 'FileIO.readall() should raise "UnsupportedOperation" when in "w" mode'
updated_at = <Date 2022-01-24.17:23:10.468>
user = 'https://github.com/evanWang1409'

bugs.python.org fields:

activity = <Date 2022-01-24.17:23:10.468>
actor = 'iritkatriel'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)', 'IO']
creation = <Date 2020-07-20.21:14:00.553>
creator = 'Ziyi Wang'
dependencies = []
files = []
hgrepos = []
issue_num = 41352
keywords = ['patch']
message_count = 1.0
messages = ['374027']
nosy_count = 2.0
nosy_names = ['python-dev', 'Ziyi Wang']
pr_nums = ['21568']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue41352'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

Linked PRs

gh-85524: Raise "UnsupportedOperation" on FileIO.readall #141214

Here are the two test cases: the one with FileIO.readall() fails

def testReadWithWritingMode(self):
    r, w = os.pipe()
    w = os.fdopen(w, "w")
    w.write("hello")
    w.close()
    with io.FileIO(r, mode="w") as f:
        with self.assertRaises(_io.UnsupportedOperation):
            f.read()

def testReadallWithWritingMode(self):
    r, w = os.pipe()
    w = os.fdopen(w, "w")
    w.write("hello")
    w.close()
    with io.FileIO(r, mode="w") as f:
        with self.assertRaises(_io.UnsupportedOperation):
            f.readall()

With FileIO.read() raises "UnsupportedOperation" in "w" mode, I expect FileIO.readall() do the same. But in fact FileIO.readall() does not check for readable and does not raise "UnsupportedOperation" in "w"mode.

I'm happy to write a pull request if you want.

pythongh-85524: Raise "UnsupportedOperation" on FileIO.readall

gh-85524: Raise "UnsupportedOperation" on FileIO.readall (#141214)

Fixed by 6f988b0.

pythongh-85524: Raise "UnsupportedOperation" on FileIO.readall (pytho…

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FileIO.readall() should raise "UnsupportedOperation" when in "w" mode #85524

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FileIO.readall() should raise "UnsupportedOperation" when in "w" mode #85524

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evanWang1409 commented on Jul 20, 2020

vstinner commented on Nov 12, 2025

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