Missing stub entry for fractions._RATIONAL_FORMAT leads to mypy error

[sr-murthy]

The stub file for the fractions standard library is missing an entry for _RATIONAL_FORMAT, which is a compiled regular expression.

I'm using libraries which import _RATIONAL_FORMAT:

...
from fractions import _RATIONAL_FORMAT
...

but running mypy against them leads to this error:

error: Module "fractions" has no attribute "_RATIONAL_FORMAT"  [attr-defined]

Is it not possible to add an entry for _RATIONAL_FORMAT? It is private, but really useful when validating numeric strings.

I saw some relevant discussion on this type of error in the mypy repo, but the solution proposed there does not work for me - it was to rewrite that particular import as an aliased import (using as), and setting the config. option implicit_reexport to true in [tool.mypy] in my project TOML. But that does not work.

My [tool.mypy] section in the project TOML looks like this:

[tool.mypy]
python_version = 3.12
mypy_path = "src"
namespace_packages = true
disallow_incomplete_defs = true
disallow_untyped_defs = true
disallow_untyped_decorators = true
exclude = "version.py"
explicit_package_bases = true
follow_imports = "silent"
ignore_missing_imports = true
implicit_reexport = true

I'm using mypy version 1.9.0 and Python 3.11.2.

[srittau]

We accept private fields on request. Please just open a PR if you want to add this to the module. Per our policy, I'm going to close this issue in the meantime.

[sr-murthy]

Np, will open a PR.