Don't access the module dictionary directly

[erlend-aasland]

BPO	42243
Nosy	@rhettinger, @serhiy-storchaka, @erlend-aasland
PRs	bpo-42243: Use PyModule_Add*() in _sre iso. direct module dict manipulation #23101

^{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 = <Date 2020-12-28.22:36:54.657>
created_at = <Date 2020-11-02.08:20:25.517>
labels = ['type-feature', 'library', '3.10']
title = "Don't access the module dictionary directly"
updated_at = <Date 2020-12-28.22:36:54.657>
user = 'https://github.com/erlend-aasland'

bugs.python.org fields:

activity = <Date 2020-12-28.22:36:54.657>
actor = 'erlendaasland'
assignee = 'none'
closed = True
closed_date = <Date 2020-12-28.22:36:54.657>
closer = 'erlendaasland'
components = ['Library (Lib)']
creation = <Date 2020-11-02.08:20:25.517>
creator = 'erlendaasland'
dependencies = []
files = []
hgrepos = []
issue_num = 42243
keywords = ['patch']
message_count = 4.0
messages = ['380197', '380198', '380200', '380247']
nosy_count = 3.0
nosy_names = ['rhettinger', 'serhiy.storchaka', 'erlendaasland']
pr_nums = ['23101']
priority = 'normal'
resolution = 'wont fix'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue42243'
versions = ['Python 3.10']

[erlend-aasland]

Quoting from https://docs.python.org/3.10/c-api/module.html:
"It is recommended extensions use other PyModule_* and PyObject_* functions rather than directly manipulate a module’s __dict__."

A number of modules still access the module dictionary directly:
zsh % grep -r PyModule_GetDict Modules
Modules/errnomodule.c: PyObject *module_dict = PyModule_GetDict(module);
Modules/_sre.c: d = PyModule_GetDict(m);
Modules/_cursesmodule.c: d = PyModule_GetDict(m);
Modules/_threadmodule.c: d = PyModule_GetDict(m);
Modules/signalmodule.c: PyObject *d = PyModule_GetDict(m);
Modules/_xxsubinterpretersmodule.c: PyObject *ns = PyModule_GetDict(main_mod); // borrowed
Modules/_xxsubinterpretersmodule.c: PyObject *ns = PyModule_GetDict(module); // borrowed
Modules/socketmodule.c: dict = PyModule_GetDict(m);
Modules/_ssl.c: d = PyModule_GetDict(m);
Modules/_curses_panel.c: PyObject *d = PyModule_GetDict(mod);
Modules/_sqlite/connection.c: module_dict = PyModule_GetDict(module);
Modules/_winapi.c: PyObject *d = PyModule_GetDict(m);
Modules/pyexpat.c: d = PyModule_GetDict(m);

[serhiy-storchaka]

Are all these occurrences in the module initialization code?

I think there is nothing wrong with this. Yes, the code can be a little clearer if use PyObject_GetArrt or PyModule_Add*, but rewriting can introduce new bugs.

The remark in the documentation is rather about reading the module attributes and writing a new code. It does not require rewriting existing code.

You can do this, but it will be treated as pure cosmetic change. It can be accepted if the new code is much clearer.

[erlend-aasland]

Are all these occurrences in the module initialization code?

Most of them, but not all.

but rewriting can introduce new bugs.

Of course.

You can do this, but it will be treated as pure cosmetic change. It can be accepted if the new code is much clearer.

It mostly results in more compact code, which, in my opinion, would improve both readability and maintainability.

[rhettinger]

I would leave it as-is.