Module 0: Your First Program

0.5 Exercise: Download whackamole.py into your module0 folder. Then open it and run it. You should see

The purpose of the program and how you use it should be easy to figure out.

Let's point out a few things:

• Unlike the toy helloworld.py example, this program actually does something nontrivial.

• The program brings up a window, and allows a user to interact with it (the program).

Now let's list the program and then point out some "surface" features.

The full program:

# whackamole with nerf gun

# Use programs written by others through "import"
import tkinter as tk  

# Define a window
window = tk.Tk()

# The instructions at the top
instructions = 'Click reset, then click fire to strike the mole'
label = tk.Label(text=instructions)
label.pack()

# Build a rectangular space on which to draw 
# shapes like circles
w = 300
h = 200
canvas = tk.Canvas(master=window, width=w, height=h)
canvas.pack()

# These are variables that control the 
# position of the target and nerf ball
targetX = 0
targetVX = 10
nerfX = 0
nerfY = h-10
nerfVX = 20
nerfVY = 0
nerfAY = -3
delT = 0.1
nerfFired = False


# This is what we want to do when the 
# reset button is clicked:
def reset():
    global nerfFired, targetX, nerfX, nerfY, nerfVY
    nerfFired = False
    targetX = 0
    nerfX = 0
    nerfY = h-1
    nerfVY = 0
    canvas.delete("all")
    print('reset')

# When the fire button is clicked, we change 
# the status of the nerf gun
def fire():
    # start launch
    global nerfFired
    nerfFired = True
    print('fired')

# Build the three buttons called "reset", "fire" and "quit"
frame = tk.Frame(master=window)
frame.pack()

resetb = tk.Button(
    master=frame, text="reset", relief=tk.RIDGE, 
    fg='black', bg='grey', height=2, width=5,command=reset)
resetb.grid(row=0, column=0)

fireb = tk.Button(
    master=frame, text="fire", relief=tk.RIDGE, 
    fg='black', bg='grey', height=2, width=5, command=fire)
fireb.grid(row=0, column=1)

quitb = tk.Button(
    master=frame, text="quit", relief=tk.RIDGE, fg='black', 
    bg='grey', height=2, width=5, command=window.destroy)
quitb.grid(row=0, column=2)

# This part of the code draws and animates
def run():
    global targetX, nerfX, nerfVY, nerfY
    canvas.delete("all")
    targetX += targetVX * delT
    canvas.create_rectangle(
        targetX, h-10, targetX+10, h, fill="green")
    if nerfFired:
        nerfX += nerfVX * delT
        nerfVY += nerfAY * delT
        nerfY += nerfVY * delT
    canvas.create_oval(
        nerfX+5,h-nerfY+5, nerfX+15, h-nerfY+15, 
        fill="red")
    window.after(1, run)

# Launch the window and start the animation
window.after(1, run)
window.mainloop()
    

Yes, that's a long program! Now let's point out some features:

First, some features from the first half of the program:

And some from the latter part:

0.6    GUI vs. command-line