Function _write_atomic

Lib/importlib/_bootstrap_external.py:200–219

Best-effort function to write data to a path atomically. Be prepared to handle a FileExistsError if concurrent writing of the temporary file is attempted.

(path, data, mode=0o666)

def _write_atomic(path, data, mode=0o666):
    """Best-effort function to write data to a path atomically.
    Be prepared to handle a FileExistsError if concurrent writing of the
    temporary file is attempted."""
    # id() is used to generate a pseudo-random filename.
    path_tmp = f'{path}.{id(path)}'
    fd = _os.open(path_tmp,
                  _os.O_EXCL | _os.O_CREAT | _os.O_WRONLY, mode & 0o666)
    try:
        # We first write data to a temporary file, and then use os.replace() to
        # perform an atomic rename.
        with _io.open(fd, 'wb') as file:
            file.write(data)
        _os.replace(path_tmp, path)
    except OSError:
        try:
            _os.unlink(path_tmp)
        except OSError:
            pass
        raise


_code_type = type(_write_atomic.__code__)