Issues with for loop converting from JAVA to Python processing

Question

Hey so I was trying to practice this exercise in python, but the code was only available in java, the code goes as follows:


void setup() {
  size(640, 360);
  dim = width/2;
  background(0);
  colorMode(HSB, 360, 100, 100);
  noStroke();
  ellipseMode(RADIUS);
  frameRate(1);
}

void draw() {
  background(0);
  for (int x = 0; x <= width; x+=dim) {
    drawGradient(x, height/2);
  } 
}

void drawGradient(float x, float y) {
  int radius = dim/2;
  float h = random(0, 360);
  for (int r = radius; r > 0; --r) {
    fill(h, 90, 90);
    ellipse(x, y, r, r);
    h = (h + 1) % 360;
  }
}

I have the following code for python:

 def setup():
    size(800,800)
    background(0)
    colorMode(HSB, 360,100,100)
    noStroke()
    ellipseMode(RADIUS)
    frameRate(1)    


def draw():
    background(0)
    for x in range(0, width, x = x + width/2):
        drawGradient(x, height/2)
        
   
    
def drawGradient(a,b):
    radius = width/2
    h = random(0,360)
    for r in range(radius, 0, radius= radius - 1):
        fill(h, 90,90)
        ellipse(a,b,r,r)
        h = (h+1) % 360

I am getting the following error

UnboundLocalError: local variable 'x' referenced before assignment

shouldn't the dim be iterated backwards though, to create the radial circles? i was also confused as to how python knows the second argument, like if its less than or greater than — MATH ASKER
– MATH ASKER, Commented Sep 12, 2021 at 14:45

Rabbid76 · Accepted Answer · 2021-09-12 15:04:15Z

4

Read about the range() function and for-loops. In python a typical for loop is:

for i in range(0, 10, 1)
    print(i)

This loop prints the numbers from 0 to 9.

The correct syntax for your code is:

def draw():
    background(0)
    for x in range(0, width+1, width/2):
        drawGradient(x, height/2)

def drawGradient(a,b):
    radius = width/4
    h = random(0,360)
    for r in range(radius, 0, -1):
        # [...]

Complete example:

def setup():
    global dim
    size(640, 360)
    dim = width/2
    background(0);
    colorMode(HSB, 360, 100, 100)
    noStroke()
    ellipseMode(RADIUS)
    frameRate(1)    

def draw():
    background(0)
    for x in range(0, width+1, width/2):
        drawGradient(x, height/2)
        
def drawGradient(x, y):
    radius = dim/2
    h = random(0, 360)
    for r in range(radius, 0, -1):
        fill(h, 90, 90)
        ellipse(x, y, r, r)
        h = (h+1) % 360

edited Sep 12, 2021 at 15:04

answered Sep 12, 2021 at 14:46

Rabbid76

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