Atomic wrapper for ElementFlow

ElementFlowAtomicOutputWrapper.py

# If you create xml via ElementFlow and make some bad things (and exceptions raise)
# you will get invalid xml (only a criple part of the xml you wish to have).
#
# This is a wrapper for ElementFlow for 'atomic' xml: it either created or not.

import shutil
import tempfile

class ElementFlowAtomicOutputWrapper(object):
    def __init__(self, out_file_path):
        self.out_file_path = out_file_path


    def __enter__(self):
        self.temp_file = tempfile.NamedTemporaryFile()
        return self.temp_file


    def __exit__(self, type, value, traceback):
        self.temp_file.flush()
        shutil.copyfile(self.temp_file.name, self.out_file_path)

## Can be used like this:
# with AtomicOutputWrapper('/path/to/file') as f:
#     with elementflow.xml(f, u'some_tree') as xml: