open-file-with-context-handler (SIM115)

Derived from the flake8-simplify linter.

What it does

Checks for cases where files are opened (e.g., using the builtin open() function) without using a context manager.

Why is this bad?

If a file is opened without a context manager, it is not guaranteed that the file will be closed (e.g., if an exception is raised), which can cause resource leaks.

Preview-mode behavior

If [preview] mode is enabled, this rule will detect a wide array of IO calls where context managers could be used, such as tempfile.TemporaryFile() or tarfile.TarFile(...).gzopen(). If preview mode is not enabled, only open(), builtins.open() and pathlib.Path(...).open() are detected.

Example

file = open("foo.txt")
...
file.close()

Use instead:

with open("foo.txt") as file:
    ...

References

• Python documentation: open