Callback Function
(Wikipedia) In computer programming, a callback is any executable code that is passed as an argument to other code, which is expected to call back (execute) the argument at a given time.
This execution may be immediate or it might happen at a later time. In all cases, the intention is to specify a function or subroutine as an entity that is (depending on the language), more or less similar to a variable.
To be simple, a "callback" is any function that is called by another function which takes the "callback" function as a parameter.
Now we are going to see how to implement a very trivial callback mechanism in Python.
def say_name():
print("Sniffy")
def say_hello(p1, callback):
print(p1)
callback()
# call say_hello with say_name as an argument
say_hello("Hello", say_name)
In the code shown above, the first function say_name()
is an ordinary function.
The second function has two parameters: the first parameter p1
is an ordinary parameter that accept a string value; the second parameter callback
is a name of a function.
We pass the function say_name
as an argument when we invoke say_hallo("Hello", say_name)
. say_name()
acts as a callback function.
As output, we’ll have:
Hello
Sniffy