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sys-exit-alias (PLR1722)

Added in v0.0.156 · Related issues · View source

Derived from the Pylint linter.

Fix is sometimes available.

What it does

Checks for uses of the exit() and quit().

Why is this bad?

exit and quit come from the site module, which is typically imported automatically during startup. However, it is not guaranteed to be imported, and so using these functions may result in a NameError at runtime. Generally, these constants are intended to be used in an interactive interpreter, and not in programs.

Prefer sys.exit(), as the sys module is guaranteed to exist in all contexts.

Fix safety

This fix is always unsafe. When replacing exit or quit with sys.exit, the behavior can change in the following ways:

  1. If the code runs in an environment where the site module is not imported (e.g., with python -S), the original code would raise a NameError, while the fixed code would execute normally.

  2. site.exit and sys.exit handle tuple arguments differently. site.exit treats tuples as regular objects and always returns exit code 1, while sys.exit interprets tuple contents to determine the exit code: an empty tuple () results in exit code 0, and a single-element tuple like (2,) uses that element's value (2) as the exit code.

Example

if __name__ == "__main__":
    exit()

Use instead:

import sys

if __name__ == "__main__":
    sys.exit()

References