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Atomic file writes.

Project description

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Atomic file writes.

Features that distinguish it from other similar libraries:

  • Race-free assertion that the target file doesn’t yet exist. This can be controlled with the overwrite parameter.
  • Windows support, although untested. The MSDN resources are not very explicit about which operations are atomic. This requires pywin32.
  • Simple high-level API that wraps a very flexible class-based API.

Usage:

from atomicwrites import atomic_write

with atomic_write('foo.txt') as f:
    f.write('Hello world.')
    # "foo.txt" doesn't exist yet.

# Now it does.

How it works

It uses a temporary file in the same directory as the given path. This ensures that the temporary file resides on the same filesystem.

The temporary file will then be atomically moved to the target location: On POSIX, it will use rename if files should be overwritten, otherwise a combination of link and unlink. On Windows, it uses MoveFileEx (see MSDN) with the appropriate flags.

Note that with link and unlink, there’s a timewindow where the file might be available under two entries in the filesystem: The name of the temporary file, and the name of the target file.

License

Licensed under the MIT, see LICENSE.

Project details


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