Change colour of screen thingy with pywebview

changer.py

import webview


class Api:
    def __init__(self):
        self.recording = False

    def record(self):
        if not self.recording:
            self.recording = True
            print('start recording')
        else:
            self.recording = False
            print('stop recording')


def evaluate_js(window):
    result = window.evaluate_js("""

function colourChanger() {
    var screen = document.body;
    if (screen.className !== 'black') {
        screen.style.backgroundColor= '#000';
        screen.className = 'black'
    }
    else {
        screen.style.backgroundColor = "#fff";
        screen.className = '';
    }
}

function startStop() {
    pywebview.api.record();
}

document.body.onkeyup = function(e){
    if (e.keyCode == 32) { // HIT SPACEBAR
	colourChanger();
    } else if (e.keyCode == 83) { // HIT S KEY
	startStop();
    }
}

        """)


if __name__ == '__main__':
    api = Api()
    window = webview.create_window('Colour Thingy', js_api=api, fullscreen=False)
    webview.start(evaluate_js, window)