temp_code/pyobjc/demo001/main.py

import objc
from AppKit import NSApplication, NSWindow, NSTextField, NSApp, NSMakeRect, NSObject

class AppDelegate(NSObject):
    def applicationDidFinishLaunching_(self, notification):
        window = NSWindow.alloc().initWithContentRect_styleMask_backing_defer_(
            NSMakeRect(0, 0, 400, 200),
            NSWindow.StyleMask.titled | NSWindow.StyleMask.closable | NSWindow.StyleMask.resizable,
            NSBackingStore.Buffered,
            False
        )
        window.center()
        window.setTitle_("Hello World App")
        window.makeKeyAndOrderFront_(None)

        label = NSTextField.alloc().initWithFrame_(NSMakeRect(0, 0, 400, 200))
        label.setStringValue_("Hello World")
        label.sizeToFit()
        label.setFrameOrigin_(NSMakePoint(0, 0))
        window.contentView().addSubview(label)

    def applicationShouldTerminateAfterLastWindowClosed_(self, sender):
        return True

if __name__ == '__main__':
    NSApplication = NSApplication.sharedApplication()
    delegate = AppDelegate.alloc().init()
    NSApplication.setDelegate_(delegate)
    NSApplication.run()