directives_version_platform error

Variable defined only in dead version/platform branch

When sys.version_info, sys.platform, or os.name is compared against a constant, one branch may be statically known to be dead for the configured target Python version (CHKARCH-VERSION-TARGET, issue #93) and platform. Variables defined exclusively in a dead branch are undefined outside that branch.

import sys

if sys.version_info < (3, 8):
    val = ""   # dead on Python 3.12
else:
    other = ""

print(val)     # E: `val` is only defined in a dead branch
print(other)   # OK

How to handle it

Every rule is on by default — strict is the default, not a cage. You can dial directives_version_platform down per-file or per-path from your editor or pyproject.toml, or fix the code so it type-checks. See the Type System rules and the complete diagnostic reference.

Canonical URL: https://www.basilisk-python.dev/errors/directives_version_platform