The system will save old log files by appending extensions to the filename.
The extensions are date-and-time based, using the strftime format
- ``%Y-%m-%d_%H-%M-%S`` or a leading portion thereof, depending on the rollover
- interval. If *backupCount* is nonzero, at most *backupCount* files will be
- kept, and if more would be created when rollover occurs, the oldest one is
- deleted.
+ ``%Y-%m-%d_%H-%M-%S`` or a leading portion thereof, depending on the
+ rollover interval. If *backupCount* is nonzero, at most *backupCount* files
+ will be kept, and if more would be created when rollover occurs, the oldest
+ one is deleted. The deletion logic uses the interval to determine which
+ files to delete, so changing the interval may leave old files lying around.
.. method:: TimedRotatingFileHandler.doRollover()