python - Swinging pendulum does not work -

i having little trouble project. have create pendulum using key handles , code have key's , down don't seem working. "up" suppose make pendulum go faster , "down" makes go slower. code have far. can please help.

from tkinter import * # import tkinter import math width = 200 height = 200 pendulumradius = 150 ballradius = 10 leftangle = 120 rightangle = 60  class maingui:     def __init__(self):         self.window = tk() # create window, may call root, parent, etc         self.window.title("pendulum") # set title          self.canvas = canvas(self.window, bg = "white",                               width = width, height = height)         self.canvas.pack()          self.angle = leftangle # start leftangle         self.angledelta = -1 # swing interval         self.delay = 200         self.window.bind("<key>",self.key)         self.displaypendulum()         self.done = false         while not self.done:             self.canvas.delete("pendulum") # used delete(all) in previous lab                                            # here delete pendulum object                                            # in displaypendulum give tag                                            # ovals , line (pendulum)             self.displaypendulum()          # redraw              self.canvas.after(self.delay) # sleep 100 milliseconds             self.canvas.update() # update canvas           self.window.mainloop() # create event loop      def displaypendulum(self):         x1 = width // 2;         y1 = 20;          if self.angle < rightangle:             self.angledelta = 1 # swing left         elif self.angle > leftangle:             self.angledelta = -1 # swing right          self.angle += self.angledelta         x = x1 + pendulumradius * math.cos(math.radians(self.angle))         y = y1 + pendulumradius * math.sin(math.radians(self.angle))          self.canvas.create_line(x1, y1, x, y, fill="blue", tags = "pendulum")         self.canvas.create_oval(x1 - 2, y1 - 2, x1 + 2, y1 + 2,                                  fill = "red", tags = "pendulum")         self.canvas.create_oval(x - ballradius, y - ballradius,                                  x + ballradius, y + ballradius,                                 fill = "green", tags = "pendulum")     def key(self,event):         print(event.keysym)         print(self.delay)         if event.keysym == 'up':            print("up arrow key pressed, delay is",self.delay)            if self.delay >10:                self.delay -= 1         if event.keysym == 'down':             print("down arrow key pressed,delay is",self.delay)             if self.delay < 200:                 self.delay += 1         if event.keysym=='q':             print ("press q")             self.done = true             self.window.destroy()      maingui() 

the root of problem event keysym "up" comparing all-lowercase "up". naturally, comparison fails every time. change if statement if event.keysym == 'up':

improving animation

in case you're interested, there better way animation in tkinter write own infinite loop. tkinter has infinite loop running (mainloop), can take advantage of that.

create function draws 1 frame, have function arrange called again @ point in future. specifically, remove entire "while" loop single call displayframe(), , define displayframe this:

def drawframe(self):     if not self.done:         self.canvas.delete("pendulum")         self.displaypendulum()         self.canvas.after(self.delay, self.drawframe) 

improving bindings

generally speaking, code marginally easier manage , test if have specific bindings specific keys. instead of single catch-all function, can have specific functions each key.

since app supports key, down key, , "q" key, recommend 3 bindings:

self.window.bind('<up>', self.onup) self.window.bind('<down>', self.ondown) self.window.bind('<q>', self.quit) 

you can define each function 1 thing:

def onup(self, event):     if self.delay > 10:         self.delay -= 1  def ondown(self, event):     if self.delay < 200:         self.delay += 1  def onquit(self, event):     self.done = true     self.window.destroy()