Python: SpooledTemporaryFile

The tempfile.SpooledTemporaryFile function operates exactly as TemporaryFile() does, except that data is spooled in memory until the file size exceeds the parameter max_size, or until the file’s fileno() method is called, at which point the contents are written to disk and operation proceeds as with TemporaryFile().

The resulting file has one additional method, rollover(), which causes the file to roll over to an on-disk file regardless of its size.

Via docs.python.org .