Update Gtk.Label in for-loop

[TimeMen]

for zahl in range(start, end+1):
                function(self, zahl, steps, counter, prim_counter)
                counter +=1

                if not numlist:
                    if not divlist:
                        if zahl > 1:
                            prim_counter += 1
                    elif divlist:
                        kpt_counter += 1
                elif numlist == divlist:
                    if (sqrt(zahl).is_integer()):
                        psq_counter += 1
                    else:
                        pt_counter +=1
                if numlist != divlist:
                    gt_counter += 1
                val = self.progressbar.get_fraction() + 1/end
                self.progressbar.set_fraction(val)

This is the code, after changing the Label to a Progressbar (as you can see.)
But it won't work too.

There's no exception, It's just not working.
Only at the end, the progressbar is completely filled.
It's only kinda bar, not a "progress"bar..