Pygtk3: object has no attribute 'cairo_create'

Question

I want to build a table in a window; then in every cell i want to put a Gtk.DrawingArea and then drawing a rectangle for everyone.

But I can't understand how to create the cairo context, because i get this error:

AttributeError: 'NoneType' object has no attribute 'cairo_create'

Here below i show you my code (it is still a prototype, but i want to learn how to bind a cairo context to the right object):

#!/usr/bin/python3  
import pygtk
pygtk.require('2.0')
import gtk

class collega_GUI:  
    def __init__(self):
            self.window = gtk.Window(gtk.WINDOW_TOPLEVEL)
            self.window.set_title("Drawing Area Example")
            self.window.connect("destroy", lambda w: gtk.main_quit())

            self.rows=3
            self.columns=3
            self.table = gtk.Table(self.rows,self.columns,True)
            self.window.add(self.table)

            self.DrawingArea_list = list()
            for i in range(self.rows*self.columns):
                self.DrawingArea_list.append(gtk.DrawingArea())

            for row in range(0,self.rows):
                for column in range(0,self.columns):
                    cr = self.DrawingArea_list[row*2+column].window.cairo_create()
                cr.set_line_width(9)
                cr.set_source_rgb(0.7, 0.2, 0.0)
                cr.rectangle(0.25, 0.25, 0.5, 0.5)
                cr.stroke()
                cr.set_source_rgb(0.5, 0.2, 0.3)
                cr.fill()
                self.table.attach(self.DrawingArea_list[row*2+column], row, row+1, column, column+1)

                self.window.show()

if __name__ == '__main__':
    prova = collega_GUI()
    gtk.main()

Answer 1

As the error message says the GdkWindow does not exist at that point, so you can't draw yet.

All the drawing should happen in the appropriate signal handler of the DrawingAreas: In GTK 2 the signal is "expose-event" and in the signal handler you should create the Cairo context and draw every time the handler is called. This answer has an example using a DrawingArea subclass (which is a sensible idea)

Just a warning, in GTK3 this part is a bit different.