Problem in Python

sharkDawg

Hi guy's,
I'm new to python and can't understand why my if statements aren't working? I'm sure its a simple enough error but i just can't spot it, any help would be great.

Heres my code:

#!/usr/bin/env python

gifdir = "/home/gifs/"

from Tkinter import *

global canvas 
global check 
global check2 
global check3 
global check4 

check = False
check2 = False
check3 = False
check4 = False

def forward(event):
    print 'f'
    global Forward
    Forward = canvas.create_image(200, 50, image=imgFwd, anchor=CENTER)
    check = True     
    
    if check2 == True:            
        canvas.delete(Reverse)
    
    if check3 == True:    
        canvas.delete(Left)    
    
    if check4 == True:
        canvas.delete(Right)


def reverse(event):
         
    print 's'
    global Reverse
    Reverse = canvas.create_image(200, 350, image=imgRev, anchor=CENTER)
    check2 = True    
    
    if check == True:             
        canvas.delete(Forward)
                        
    if check3 == True:    
        canvas.delete(Left)    
    
    if check4 == True:
        canvas.delete(Right)

def left(event):
    print'a'
    global Left    
    Left = canvas.create_image(50, 200, image=imgLef, anchor=CENTER)    
    check3 = True
    
    if check == True:    
        canvas.delete(Forward)

    if check2 == True:    
        canvas.delete(Reverse)    
    
    if check4 == True:
        canvas.delete(Right)    
    
def right(event):    
    print'd'
    global Right
    Right = canvas.create_image(350, 200, image=imgRig, anchor=CENTER)
    check4 = True    
    
    if check == True:    
        canvas.delete(Forward)

    if check2 == True:    
        canvas.delete(Reverse)
    
    if check3 == True:
        canvas.delete(Left)

def quit(event):
    print'exit'
    s.close()    
    sys.exit()

tkroot = Tk()
canvas = Canvas(width=400, height=400, bg='white')   # 0,0 is top left corner 
canvas.pack(expand=YES, fill=BOTH)                   # increases down, right 

canvas.create_oval(70, 70, 330, 330, width=2, fill='blue')
canvas.create_text(200, 200, font = 'bold', text='Robot')
imgFwd = PhotoImage(file=gifdir+"forward.gif")
imgRev = PhotoImage(file=gifdir+"forward.gif")
imgLef = PhotoImage(file=gifdir+"forward.gif")
imgRig = PhotoImage(file=gifdir+"forward.gif")

tkroot.bind('<Key-w>',forward)
tkroot.bind('<Key-a>',left)
tkroot.bind('<Key-d>',right)
tkroot.bind('<Key-s>',reverse)
tkroot.bind('<Key-Escape>',quit)
tkroot.mainloop()

sobriquet

What exactly is going wrong?

sharkDawg wrote: »

canvas.delete(Test)

That looks out of place to start.

Also I don't know Tk, but how is canvas related to tkroot?

sharkDawg

That was a typo, thanks, the issue is when say 'w' is pressed the .gif file is displayed on the canvas, but then when 's' is pressed the .gif file also appears in a different location but the original one form 'w' doesn't get deleted. The if statements don't seem to get read at all, i put print statements into them, but still got nothing

sobriquet

I'm at work so I can't really look into it properly but try declaring Forward, Reverse etc outside the keyb handlers first, ie Forward=None, as with the check variables.

Oh hang on, you added prints? The ifs will definitely be evaluated, I wouldn't doubt that. In that case look up some tutorials on using globals, the checks may be treated as constant values - I don't know tbh, I've never used globals vars like that and can't test it at the mo.

You should try to use more descriptive variable names too, check1 etc is hard to read.

sharkDawg

Ya sorry about the variable names. I see now that the if statements aren't the problem that its my global variables! When 'w' is pressed, check is assigned to True in the forward method but once it goes outside that method check reverts back to its defined False. How can this be changed?
I know its bad practice to use globals but i don't know any other way and don't have time to learn either!

Webmonkey

Know absolutely nothing with Python but has it got a 'Pass by Reference' mechanism? - quick google suggests that Python passes by reference by default?

sobriquet

sharkDawg wrote: »

Ya sorry about the variable names. I see now that the if statements aren't the problem that its my global variables! When 'w' is pressed, check is assigned to True in the forward method but once it goes outside that method check reverts back to its defined False. How can this be changed?
I know its bad practice to use globals but i don't know any other way and don't have time to learn either!

Well, to be honest I don't know off hand how to make the globals work, but without thinking it through, my first thought would be wrap the 'Robot' state up into a class, with variables for isMovingForward and methods for Forward() etc, something like:

class Robot:
	def __init__(self):
		self.isMovingForward = False
		self.isMovingBackward = False
		self.isMovingLeft = False
		self.isMovingRight = False

	def Forward(self, event):
		## Your Tk code
		self.isMovingForward = True
		
		if isMovingBackward == True:
			## Your Tk code

robot = Robot()
tkroot.bind('<Key-w>', robot.Forward) # No idea if this works

Completely untested and without warranty, no refunds. Hope if helps anyway. For future reference there's probably a cleaner way to pass in the canvas object to do your Tk code, accessing a global from within a class is ugly. Hope it helps though.

sharkDawg

Thanks for the reply guys, got it sorted. Just involved moving the global variables inside the methods, i know it not the best/proper way to do it but it works so i'm not touching it! I'll post up the code later

sharkDawg

Here it is:

#!/usr/bin/env python

gifdir = "/home/enda/gifs/"

from Tkinter import *
import tkSnack
import sys




def forward(event):
    
    print 'f'
    global check
    global Forward
    Forward = canvas.create_image(200, 50, image=imgFwd, anchor=CENTER)
    check = True     
    mysound.stop()    

    if check2 == True:            
        canvas.delete(Reverse)
    
    if check3 == True:    
        canvas.delete(Left)    
    
    if check4 == True:
        canvas.delete(Right)

    if check5 == True:
        canvas.delete(Stop)



def reverse(event):
    print 's'
    global check2
    global Reverse
    Reverse = canvas.create_image(200, 350, image=imgRev, anchor=CENTER)
    mysound.play()    
    check2 = True    
    
    if check == True:             
        canvas.delete(Forward)
                        
    if check3 == True:    
        canvas.delete(Left)    
    
    if check4 == True:
        canvas.delete(Right)

    if  check5 == True:
        canvas.delete(Stop)
    


def left(event):
    print'a'
    global check3
    global Left    
    mysound.stop()    
    Left = canvas.create_image(50, 200, image=imgLef, anchor=CENTER)    
    check3 = True
    
    if check == True:    
        canvas.delete(Forward)

    if check2 == True:    
        canvas.delete(Reverse)    
    
    if check4 == True:
        canvas.delete(Right)

    if check5 == True:
        canvas.delete(Stop)    


    
def right(event):    
    print'd'
    global check4
    global Right
    mysound.stop()    
    Right = canvas.create_image(350, 200, image=imgRig, anchor=CENTER)
    check4 = True    
    
    if check == True:    
        canvas.delete(Forward)

    if check2 == True:    
        canvas.delete(Reverse)
    
    if check3 == True:
        canvas.delete(Left)

    if check5 == True:
        canvas.delete(Stop)


 

def stop(event):    
    print'p'
    global check5
    global Stop
    mysound.stop()    
    Stop = canvas.create_image(200, 200, image=imgRig, anchor=CENTER)
    check5 = True    
    
    if check == True:    
        canvas.delete(Forward)

    if check2 == True:    
        canvas.delete(Reverse)
    
    if check3 == True:
        canvas.delete(Left)

    if check4 == True:
        canvas.delete(Right)



def quit(event):
    print'exit'
    sys.exit()


tkroot = Tk()
check = False
check2 = False 
check3 = False
check4 = False
check5 = False
 
canvas = Canvas(width=400, height=400, bg='white')   # 0,0 is top left corner 
canvas.pack(expand=YES, fill=BOTH)                   # increases down, right 

canvas.create_oval(70, 70, 330, 330, width=2, fill='blue')

imgFwd = PhotoImage(file=gifdir+"forward.gif")
imgRev = PhotoImage(file=gifdir+"forward.gif")
imgLef = PhotoImage(file=gifdir+"forward.gif")
imgRig = PhotoImage(file=gifdir+"forward.gif")
imgStp = PhotoImage(file=gifdir+"forward.gif")

labelfont = ('helvetica',20,'bold')
widget = Label(canvas, text='Robot', fg='white', bg='black', font = labelfont)
canvas.create_window(200, 200, window=widget)

tkSnack.initializeSnack(tkroot)
global mysound
mysound = tkSnack.Sound()
mysound.read('/home/enda/gifs/1.mp3')


tkroot.bind('<Key-w>',forward)
tkroot.bind('<Key-a>',left)
tkroot.bind('<Key-d>',right)
tkroot.bind('<Key-s>',reverse)
tkroot.bind('<Key-p>',stop)
tkroot.bind('<Key-Escape>',quit)

tkroot.mainloop()