I feel like I end up reading this once a year, usually when I'm trying to write a [python] script that needs to run from a cron script without clobbering its own files if one instance is started before the previous one is finished.

See also my shelfcache Python3 package which provides a thread- and multiprocess-safe key-value caching store on top of the standard library's shelve module: https://github.com/cristoper/shelfcache