The core of Blinker isquite small but provides powerful features:

a global registry of named signals
anonymous signals
custom name registries
permanently or temporarily connected receivers
automatically disconnected receivers via weak referencing
sending arbitrary data payloads
collecting return values from signal receivers
thread safety

link: https://pythonhosted.org/blinker/
http://flask.pocoo.org/docs/0.12/api/#flask.ctx.RequestContext.push