python - NoneType Error self.widget.insert

Question

I am trying to have an output frame in my application. When I run it i get the error: NoneType object has no attribute insert on self.widget.insert('end', string). Any help would be appreciated.

import Tkinter as tk
import sys

class Test(tk.Tk):
    def __init__(self):
        tk.Tk.__init__(self)
        toolbar = tk.Frame(self).grid()
        tk.Button(self, text="print to stdout", command=self.print_stdout).grid()

        self.text= tk.Text(self).grid()
        sys.stdout= Output(self.text)


    def print_stdout(self):
        print "Hello"
        print "This is test"

class Output(object):
    def __init__(self, widget):
        self.widget = widget

    def write(self,string):
        self.widget.insert('end', string)

app = Test()
app.mainloop()

Answer 1

Your problem occurs on this line:

self.text= tk.Text(self).grid()

grid doesn't explicitly return anything, so this is effectively setting self.text = None. This value is then passed to Output.__init__ and eventually accessed in write.

Split it into two steps instead:

 self.text = tk.Text(self)
 self.text.grid()