甲班if,elif判斷

from tkinter import * #或者import tkinter as tk
import math#輸入數學MATH函式庫
tk = Tk()           #建構視窗名為tk
tk.geometry('1200x400')#視窗 寬1200像素
tk.title("劉任昌python tkinter三角函數if_else判斷")
canvas = Canvas(tk, width=1200, height=400, bg='PINK')
canvas.grid(row=0,column=0,padx=5,pady=5,columnspan=3)
delay=1 # milliseconds, 1/1000秒
x1,y1,z1=0,200,10#python特徵,多變數=對等值
h=190      #上下範圍,相當於數學1到-1
def LH():
    global x1, y1, z1, inc #global全球,local當地
    if (x1==0): #判斷是否到達左端,==判斷是否相等
        inc = 1 #則開始往左+1步, =給值
        canvas.delete('all')
    elif (x1==1200):#否則else判斷是否到達右端
        inc = - 1   #則開始往右-1步
        canvas.delete('all')
    x2 = x1 + inc #換到下個+1,-1往右
    y2=200 - h*math.sin(0.02*x2)
    z2=200 - h*math.cos(0.02*x2)
    L1=canvas.create_line(x1,y1,x2,y2,fill='BLUE',width=10)
    L2=canvas.create_line(x1,z1,x2,z2,fill='yellow',width=10) 
    x1, y1, z1 = x2, y2, z2
    canvas.after(delay,LH)#return沒你的事,滾回你老家
LH()            #執行LauHou老猴
tk.mainloop()