mouse not recognised in class

appinv

putting

**_class Ball: x=0 y=mouseY

ball = Ball()_**

at the top of a program tells me that mouseY not recognised. Why?

GoToLoop

https://Forum.Processing.org/two/discussion/15473/readme-how-to-format-code-and-text

• The way you've written them, both x & y are static variables of class Ball, not instance. =;
• In Python, instance (non-static) members are prefixed w/ their method's 1st parameter.
• Let's say you've got a method called display(). And it's 1st parameter is named as b:
  display(b): ellipse(b.x, b.y, width>>1, height>>1)
• Also, the appropriate place to initialize instance variables is inside constructor __init()__: L-)
  __init(b)__: b.x = 0; b.y = mouseY
• Although I've used b as the name of the 1st parameter for the class' methods above, the "pythonic" way is always name them as self. ;;)
  __init(self)__: self.x = 0; self.y = mouseY

appinv

actually i know py. well my question is : how do you declare the keyword inside the class

the way i wrote that was to pose the question. Actually self.x is not more pythonic. it depends on your reasons. i specifically needed static variables for quick prototyping. again init ... hum please this is a processing forum not python one

GoToLoop

I specifically needed static variables for quick prototyping.

• Variable mouseY ISN'T static! It is an instance member of class PApplet. #-o
• class PApplet is automatically instantiated by the "sketch" itself. :-bd
• However, that happens later on, a little before invoking the 1st callback preload(). :-B
• The moment the static members of your class are initialized is too early. :-O

GoToLoop

Actually I know py. well.
The way I wrote that was to pose the question.

• A big portion of the folks who come here everyday doesn't even know the basic. :-<
• We can only judge by the way the code is presented at face-value. 3:-O
• So, when I've spotted the members x & y in your Ball class were static, I've concluded that was unintentional. /:)
• BtW, you haven't yet edited your post in order to format it in accordance to markdown: :-@

https://Forum.Processing.org/two/discussion/15473/readme-how-to-format-code-and-text

GoToLoop

Actually self.x is not more pythonic.

• I dunno much Python. Just enough to convert Java Mode to Python Mode safely. ~O)
• But AFAIK, even though self isn't a Python keyword, it is a "sacred" naming convention. :@)

appinv

no of course mouseY is not static. x and y is.

GoToLoop

But you're attempting to initialize your static variable y using the current value of an instance variable! :-@

Under Java, that wouldn't even compile! It'd display the following compile error: :-&
Cannot make a static reference to the non-static field mouseY

void setup() {
  println(new Ball().y);
  exit();
}

static class Ball {
  //static int x = WINDOWS, y = LINUX; // This 1 compiles.
  static int x = MACOSX, y = mouseY; // This 1 won't!
}

However it compiles when other static fields, like WINDOWS, LINUX & MACOSX, etc., are used instead. :>

GoToLoop

I know Python doesn't prohibit (or even knows their diff.) static members to use instance members. :-\"

But as I've already pointed out, mouseY doesn't even exist at the time you're attempting to assign it to static member Ball::y. 8-}

appinv

XD you added more emojies etc since last visit ^^

kfrajer

Related: https://forum.processing.org/two/discussion/comment/122852/#Comment_122852

The best practice is to init your variables within setup().

Kf