8000 The sys.float_repr_style should be read-only · Issue #128017 · python/cpython · GitHub
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skirpichev opened this issue Dec 17, 2024 · 13 comments
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The sys.float_repr_style should be read-only #128017

skirpichev opened this issue Dec 17, 2024 · 13 comments
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docs Documentation in the Doc dir type-bug An unexpected behavior, bug, or error

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@skirpichev
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skirpichev commented Dec 17, 2024 •
edited by bedevere-app bot
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Bug report

Bug description:

It's possible to "change" the repr style for floats:

Python 3.14.0a2+ (heads/long_export-decimal:4bb9ad04f5, Dec 17 2024, 05:39:57) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.float_repr_style
'short'
>>> sys.float_repr_style = 'legacy'
>>> sys.float_repr_style
'legacy'

Of course, this has no effect, as this variable just shows build-time settings. That certainly can misguide people, e.g. see this: #128005 (comment)

It could be nice to make this variable read-only (unfortunately, PEP 726 was rejected and it's might be not so easy). Or, at least, improve docs to mention that it's intended to be read-only (we emphasize this e.g. for int_info fields).

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

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@skirpichev skirpichev added the type-bug An unexpected behavior, bug, or error label Dec 17, 2024
@srinivasreddy
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srinivasreddy commented Dec 17, 2024 •
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@skirpichev Are you working on it? Shall i take it?
8000

@srinivasreddy
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So final resolution is to improve the docs that float_repr_style is only a read only field, and that any change to other values such as legacy has no effect on the formatting?

@picnixz picnixz added interpreter-core (Objects, Python, Grammar, and Parser dirs) extension-modules C modules in the Modules dir and removed extension-modules C modules in the Modules dir labels Dec 17, 2024
@skirpichev
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Are you working on it?

No. I'm not sure yet how it should be solved.

Shall i take it?

Sure.

So final resolution is to improve the docs that float_repr_style is only a read only field

The "problem" actually span not only this variable in the sys module. You can "change" everything:

>>> sys.maxsize
9223372036854775807
>>> sys.maxsize = 123
>>> sys.maxsize
123
>>> sys.int_info = "Spam"
>>> sys.int_info
'Spam'

Current docs looks ok for me. But it seems some people are misguided by such possibility. Maybe some generic note might help them.

@vstinner
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https://peps.python.org/pep-0726/ was a good solution to this problem but it was rejected: https://discuss.python.org/t/pep-726-module-setattr-and-delattr/32640

@vstinner
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It could be nice to make this variable read-only

I don't think that we can easily solve this issue and I suggest to close it.

@skirpichev
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@vstinner, does it make sense for you as a documentation issue?

@vstinner
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Which kind of documentation addition are you thinking about? Add a note to each sys attribute? Add a global note to the sys module documentation?

@skirpichev
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Add a global note to the sys module documentation?

Yes, something like

diff --git a/Doc/library/sys.rst b/Doc/library/sys.rst
index dd6293c722..1aedb277ef 100644
--- a/Doc/library/sys.rst
+++ b/Doc/library/sys.rst
@@ -8,7 +8,9 @@
 
 This module provides access to some variables used or maintained by the
 interpreter and to functions that interact strongly with the interpreter. It is
-always available.
+always available.  Except when explicitly noted otherwise, all variables are
+only for read access.
+
 
 
 .. data:: abiflags

@skirpichev skirpichev added docs Documentation in the Doc dir and removed interpreter-core (Objects, Python, Grammar, and Parser dirs) labels Dec 18, 2024
@vstinner
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sys.path is a list and so is mutable. Does modifying sys.path content count as treating sys.path as read-only or not?

Well, sys.path doc says:

A program is free to modify this list for its own purposes.

@skirpichev
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And that fails to "when explicitly noted otherwise" :-) I'm not insist on exact wording as proposed above. Does it make sense for you?

@vstinner
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You can add this sentence if it matters to you:

Except when explicitly noted otherwise, all variables are only for read access.

@skirpichev
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@srinivasreddy?

srinivasreddy added a commit to srinivasreddy/cpython that referenced this issue Jan 15, 2025
@srinivasreddy
pythongh-128017: Make a note that variables that are provided by :mod…
9729848 
…ule: sys are read-only, Unless explicitly stated otherwise
@bedevere-app bedevere-app bot mentioned this issue Jan 15, 2025
Merged
vstinner pushed a commit that referenced this issue Jan 16, 2025
@srinivasreddy
gh-128017: Make a note that sys variables are read-only (#128887)
313b96e
miss-islington pushed a commit to miss-islington/cpython that referenced this issue Jan 16, 2025
@srinivasreddy @miss-islington
pythongh-128017: Make a note that sys variables are read-only (python…
34dd8bf 
…GH-128887)

(cherry picked from commit 313b96e)

Co-authored-by: Srinivas Reddy Thatiparthy (తాటిపర్తి శ్రీనివాస్  రెడ్డి) <thatiparthysreenivas@gmail.com>
@bedevere-app bedevere-app bot mentioned this issue Jan 16, 2025
Merged
miss-islington pushed a commit to miss-islington/cpython that referenced this issue Jan 16, 2025
@srinivasreddy @miss-islington
pythongh-128017: Make a note that sys variables are read-only (python…
ce6a92f 
…GH-128887)

(cherry picked from commit 313b96e)

Co-authored-by: Srinivas Reddy Thatiparthy (తాటిపర్తి శ్రీనివాస్  రెడ్డి) <thatiparthysreenivas@gmail.com>
@bedevere-app bedevere-app bot mentioned this issue Jan 16, 2025
Merged
@vstinner
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Issue fixed the in documentation by change 313b96e.

vstinner pushed a commit that referenced this issue Jan 16, 2025
@miss-islington @srinivasreddy
[3.12] gh-128017: Make a note that sys variables are read-only (GH-12…
1c85f1b 
…8887) (#128909)

gh-128017: Make a note that sys variables are read-only (GH-128887)
(cherry picked from commit 313b96e)

Co-authored-by: Srinivas Reddy Thatiparthy (తాటిపర్తి శ్రీనివాస్  రెడ్డి) <thatiparthysreenivas@gmail.com>
hugovk pushed a commit that referenced this issue Jan 17, 2025
@miss-islington @srinivasreddy
[3.13] gh-128017: Make a note that sys variables are read-only (GH-12…
6101
9974e71 
…8887) (#128908)

Co-authored-by: Srinivas Reddy Thatiparthy (తాటిపర్తి శ్రీనివాస్  రెడ్డి) <thatiparthysreenivas@gmail.com>
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