How to make file creation an atomic operation?

Write data to a temporary file and when data has been successfully written, rename the file to the correct destination file e.g

with open(tmpFile, 'w') as f:
    f.write(text)
    # make sure that all data is on disk
    # see http://stackoverflow.com/questions/7433057/is-rename-without-fsync-safe
    f.flush()
    os.fsync(f.fileno())    
os.replace(tmpFile, myFile)  # os.rename pre-3.3, but os.rename won't work on Windows

According to doc http://docs.python.org/library/os.html#os.replace

Rename the file or directory src to dst. If dst is a non-empty directory, OSError will be raised. If dst exists and is a file, it will be replaced silently if the user has permission. The operation may fail if src and dst are on different filesystems. If successful, the renaming will be an atomic operation (this is a POSIX requirement).

Note:

  • It may not be atomic operation if src and dest locations are not on same filesystem

  • os.fsync step may be skipped if performance/responsiveness is more important than the data integrity in cases like power failure, system crash etc

Leave a Comment

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)