python - Global name 'start' is not defined: Tkinter -

i getting error "global name 'start' not defined" code snippet below. start(panel) call in displayimage(img) causes image want see displayed in gui; without no image shows up; must doing something. yet above error. i'm running program in ubuntu 12.04. btw, new both python , tkinter. way rid of error? edit: adding of image occurs during runtime button click calls loadpicture(file).

import numpy np tkinter import * import cv2 cv tkfiledialog import askopenfilename import tksimpledialog td import math mt pil import imagetk, image   ### general functions #############################################    def raisefilechooser():     global filename     filename = askopenfilename()     loadpicture(filename)  def loadpicture(file): # set global variable other uses     global img     img = cv.imread(file, 1)      img = cv.cvtcolor(img, cv.color_rgb2bgr)      displayimage(img, display1)     def displayimage(image, panel):     temp = image.fromarray(image)     bk = imagetk.photoimage(temp)     bklabel = label(display1, image = bk)     bklabel.place(x=0, y=0, relwidth=1, relheight=1)     start(panel)  ### start app ###########################################  #### gui started root = tk() np.set_printoptions(threshold=np.nan)  # can print entire arrays  ### global variables #################################### relstatus = stringvar() relstatus.set(none) text = stringvar() filepath = stringvar() filename = "no file chosen" img = none gsc = none estatus = stringvar() estatus.set(none) display1 = none display2 = none  ### gui ################################################# root.title("picture transformer") root.geometry("700x600")  app = panedwindow(root) app.pack(padx=20, pady=20)  #button panel############## buttonpanel = frame(app,width=200, height = 400) buttonpanel.pack(side=left)  chooser = button(buttonpanel, text="choose file", height=1, width=9, command=raisefilechooser) chooser.pack()  #set display panels ########################### display1 = frame(app, width=900, height=900, bg="#cccccc") display1.pack(side=left, fill=both, expand=1)  root.mainloop() 

edit: stacktrace:

traceback (most recent call last): file "/usr/lib/python2.7/lib-tk/tkinter.py", line 1413, in __call__ return self.func(*args) file "hw2.py", line 78, in raisefilechooser loadpicture(filename) file "hw2.py", line 86, in loadpicture start(panel) nameerror: global name 'start' not defined 

the error telling what's wrong -- there no global start function in code. in fact, near can tell, there's no start method anywhere, in object creating. why think should calling function named start? there documentation somewhere telling this?

my guess is, you're running in idle, , when call non-existent start function, script crashes. when script crashes returns idle, , whatever windows had created point visible.

the obvious problem have in code aren't creating root window. somewhere in script, before create widgets or instances of stringvar need this:

root = tk()