PYObjC NSWindow is NoneType?

Question

window = NSApplication.sharedApplication().mainWindow()
    window.contentView().addSubview_(chart_view)

The window was made in another section and appears fine but I get this:

: 'NoneType' object has no attribute 'contentView'

Does anyone know why it thinks the window is "NoneType"? Thankyou.

Answer 1

It looks like mainWindow() is returning None, which suggests that there is no active window or something like that.