ruff/crates/ty_python_semantic/resources/mdtest/sys_platform.md

sys.platform

Explicit selection of all platforms

When python-platform="all" is specified, we fall back to the type of sys.platform declared in typeshed:

[environment]
python-platform = "all"

import sys

reveal_type(sys.platform)  # revealed: LiteralString

Explicit selection of a specific platform

[environment]
python-platform = "linux"

import sys

reveal_type(sys.platform)  # revealed: Literal["linux"]

Testing for a specific platform

[environment]
python-platform = "freebsd8"

Exact comparison

import sys

reveal_type(sys.platform == "freebsd8")  # revealed: Literal[True]
reveal_type(sys.platform == "linux")  # revealed: Literal[False]

Substring comparison

It is recommended to use sys.platform.startswith(...) for platform checks:

import sys

reveal_type(sys.platform.startswith("freebsd"))  # revealed: Literal[True]
reveal_type(sys.platform.startswith("linux"))  # revealed: Literal[False]