Modern Python Standard Library Cookbook

How to do it...

You need to perform the following recipes:

1. Much like open can be used as a context manager, we can easily roll out a safe_open function that allows us to open a file for writing in a safe way:

import tempfile, os

class safe_open:
    def __init__(self, path, mode='w+b'):
        self._target = path
        self._mode = mode

    def __enter__(self):
        self._file = tempfile.NamedTemporaryFile(self._mode, delete=False)
        return self._file

    def __exit__(self, exc_type, exc_value, traceback):
        self._file.close()
        if exc_type is None:
            os.rename(self._file.name, self._target)
        else:
            os.unlink(self._file.name)

2. Using safe_open as a context manager allows us to write to the file pretty much like we would normally:

with safe_open('/tmp/myfile') as f: f.write(b'Hello ...