[Tutor] Please explain part of this code

[Jim]

On 02/15/2017 04:56 PM, Alan Gauld via Tutor wrote:
> On 15/02/17 22:37, Jim wrote:
>
>>          self.choices = {
>>                  "1": self.show_notes,
>>                  "2": self.search_notes,
>>                  "3": self.add_note,
>>                  "4": self.modify_note,
>>                  "5": self.quit
>>                  }
>>
>> The author says:
>>
>> The action variable actually refers to a specific method and is called
>> by appending empty brackets (since none of the methods require
>> parameters) to the variable.
>>
>
>> I don't recall ever seeing this before.  What is this technique called?
>
> Its very common, especially in GUIs and used in many
> languages including C, VB, Java, Javascript and Lisp.
> Its usually called a callback (because the stored
> function is called back by the event receiver).
>
> In C it is done by using a "pointer to a function".
> In Lisp you create a Lambda (an anonymous function)
> - which you can also do in Python and recent Java
> versions. In Smalltalk and Ruby you define a "block".
> In most of the other languages it's similar to Python,
> you just pass the name of the function.
>
> This is often referred to as the language treating
> functions as "first class objects", and is a core
> part of Functional Programming.
>
> A common FP structure is the map function which takes
> a function and a sequence and applies the function
> to each member of the sequence, returning the
> resultant sequence. Here is a short Python example:
>
> def double(x): return x*2
>
> data = [1,2,3,4]
> result = map(double, data)   # -> [2,4,6,8]
> print(result)
>
> HTH
>
It does help. I have done a little bit of tkinter programing and have 
used callbacks, but when I looked at this code it just didn't register 
that way in my mind. Thanks for your explanation.

Regards,  Jim