A
callback is a function that's called from within another, having initially been "registered" for use at an outer level earlier on.
Yeah, right - what does that mean or do?
An example ... if I'm setting up a GUI (Graphic User Interface), as I define my various sliders and buttons, I want to say "when this is pressed, do xxxx", but I don't actually want to do "xxxx" until the button is pressed - probably some considerabel time after the initial definition.
An example from this week's
Python Course - see
[here].
I've defined a couple of methods for running later such as:
def inflate(value):
return value * 1.7
I've passed those methods into an object
john = thing(12,inflate)
and used a method I've chosen to call "perform" to run the method later:
print(john.perform())
To complete the example, here's the class:
class thing:
def __init__(this,amount,action):
this.amount = amount
this.action = action
def perform(this):
return this.action(this.amount)
(written 2016-02-11, updated 2016-02-12)
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