Function ?

[iDweadith]

Guys can you explain what is Function() used for?

action(Function())

[drKlauz]

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textbutton "Click me" action Function(print,"clicked!")

Used to call existing function in cases where builtin actions are not enough.
First argument is function (any callable should work, tho doubt it will work properly with lambdas), rest are arguments supplied to this function.
https://www.renpy.org/doc/html/screen_a ... l#Function

Common use cases:
- changing lots of variables
- showing/hiding lots of screens
- doing something if result of some calculations is right

[gas]

Above is right.

For the VERY newbie...
A function is a snippet of PYTHON code that process some line, usually getting an input and throwing an output.
The function can then be called at will to do repetitive stuff.

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init python:
    def dice_roll(min,max):
        return renpy.random.randint(min,max)

you've created a function called 'dice_roll'. The function do nothing until you'll use it and pass any value required. Now you can use it at will when needed.
As you can see, it require two parameters, min and max, that you must give when calling the function, and return something (in that case, the random range between them).

So you can do:

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$ dice = dice_roll(1,6)

and now 'dice' is the function return, so a number from 1 to 6.
Python is smart enough to compute the function immediatedly if you'll quote it, so you can do something like...

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if dice_roll(1,6) >3:
    e "You rolled above 3!"

If you don't set any 'return', the function automatically return 'None' on his own.

NOW, a function can also operate on global variables. So for example return nothing but manipulate some value when called.

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default counter = 0
init python:
    def update():
        counter +=1

label start:
    e "Enter a loop!"
label loop:
    $ update()
    e "The value is now [counter]!"
    jump loop

As you can see there's no 'return' and no parameter, the function simply add 1 to an existing variable and return 'None' (no value to store somewhere in the end).

The Function() action work like this. Call a function, operate on some global variable and return 'None'.

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default score = 0

init python:
    def update_score(amount):
        score += renpy.random.randint(1*amount,6*amount)

screen myscreen():
    imagebutton auto "img_%s.png" action Function(update_score, 3)

Clicking on the button add the roll of 3 six faced die to the score. And that's all.

NOW, if you instead of showing you CALLED the screen, the Function action is like a Return(), that close the screen and _return the function output.
So, in the above case, you can do:

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    call screen mydie()
    $ dice = _return

If you think is a mess, IT'S complicated and probably the more complicated action you can use in a screen.