A quick disclaimer: I'm a bit of a newbie, so this issue might be just me not seeing the obvious, but basically when I run in Processing I get the following error: Interestingly enough, I am only returned the error when any one of Processing's built in functions (such as setup(), draw() or mouseClicked) is defined as well, so if

Why am I getting a NullPointerException for strokeWeight() in Processing.py?

A quick disclaimer: I’m a bit of a newbie, so this issue might be just me not seeing the obvious, but basically when I run

def setup():
    size(400,400)

def test():
    strokeWeight(5)
    circle(100, 100, 100)

test()

in Processing I get the following error:

processing.app.SketchException: java.lang.NullPointerException
at processing.core.PApplet.strokeWeight(PApplet.java:14431)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.python.core.PyReflectedFunction.__call__(PyReflectedFunction.java:188)
    at org.python.core.PyReflectedFunction.__call__(PyReflectedFunction.java:206)
    at org.python.core.PyObject.__call__(PyObject.java:497)
    at org.python.core.PyObject.__call__(PyObject.java:501)
    at org.python.core.PyMethod.__call__(PyMethod.java:141)
    at org.python.pycode._pyx58.test$2(sketch_210426a.pyde:6)
    at org.python.pycode._pyx58.call_function(sketch_210426a.pyde)
    at org.python.core.PyTableCode.call(PyTableCode.java:171)
    at org.python.core.PyBaseCode.call(PyBaseCode.java:139)
    at org.python.core.PyFunction.__call__(PyFunction.java:413)
    at org.python.pycode._pyx58.f$0(sketch_210426a.pyde:1)
    at org.python.pycode._pyx58.call_function(sketch_210426a.pyde)
    at org.python.core.PyTableCode.call(PyTableCode.java:171)
    at org.python.core.PyCode.call(PyCode.java:18)
    at org.python.core.Py.runCode(Py.java:1614)
    at org.python.core.Py.exec(Py.java:1658)
    at org.python.pycode._pyx57.f$0(/var/folders/vf/3zy00t252_372n6n1n060tc00000gn/T/sketch_210426a6112183873956099370/sketch_210426a.pyde:96)
    at org.python.pycode._pyx57.call_function(/var/folders/vf/3zy00t252_372n6n1n060tc00000gn/T/sketch_210426a6112183873956099370/sketch_210426a.pyde)
    at org.python.core.PyTableCode.call(PyTableCode.java:171)
    at org.python.core.PyCode.call(PyCode.java:18)
    at org.python.core.Py.runCode(Py.java:1614)
    at org.python.core.Py.exec(Py.java:1658)
    at org.python.util.PythonInterpreter.exec(PythonInterpreter.java:276)
    at jycessing.PAppletJythonDriver.processSketch(Unknown Source)
    at jycessing.PAppletJythonDriver.findSketchMethods(Unknown Source)
    at jycessing.Runner.runSketchBlocking(Unknown Source)
    at jycessing.mode.run.SketchRunner.lambda$startSketch$3(Unknown Source)
    at java.lang.Thread.run(Thread.java:748)

    at jycessing.mode.run.SketchRunner.convertPythonSketchError(Unknown Source)
    at jycessing.mode.run.SketchRunner.lambda$startSketch$3(Unknown Source)
    at java.lang.Thread.run(Thread.java:748)

Interestingly enough, I am only returned the error when any one of Processing’s built in functions (such as setup(), draw() or mouseClicked) is defined as well, so if I ran:

def why_arent_you_working():
    print("please")
    
def test():
    strokeWeight(5)
    circle(100, 100, 100)
    
test()
why_arent_you_working()

it would work for some reason.

I’ve tried 10 diffrent threads concerning NullPointerException but I just can’t seem to find what I did wrong. As I’ve prefaced this post, I am a newbie, so its probably some stupid oversight of mine but it would be great if someone helped me out.

Answer

This might be a result of “mixing active and static modes”. Active mode is when you use setup() and/or draw(), and static mode is when you don’t. Basically, if you’re using setup(), you can’t call any functions outside of an indentation (or a variable definition). The standard way to draw a circle on the screen is like this:

def setup():
    size(400,400)

def draw():
    strokeWeight(5)
    circle(100, 100, 100)

draw() is called just like setup() is: it’s automatically called without you explicitly calling it anywhere.

Keep in mind that draw() is a loop, so it will run continuously until noLoop() is called.

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Answer