Hi there folks!
After getting a wireless transceiver USB dongle to communicate with an arduino MEGA2560 from ....click here..... , I'm deciding to piece together a python script for controlling the arduiino from my desktop windows 8 computer 'PC'. After doing that, the plan is to use the script/code to move my 'zumobot' around (- ie. the little tank-like robot with rubber tracks, based on arduino UNO).
Along the way, I came across code on the internet ('stackoverflow'), that demonstrates how to make our PC keyboard detect more-than-one keyboard key being pressed - simultaneously. I tried this code (script included in this post), and it really works - with GUI 'pong' paddle graphics! It works in python 3..... I ran it with 'IDLE' software. It also works in python 2, but need to change the word 'tkinder' to capital 'Tkinder' before running it.
Now, I know basic python programming (working with arrays, file reading/writing, loops, conditional statements, serial communications etc), but certainly don't yet know about the objects or 'classes' programming. I will be working towards understanding it by gathering information.
A couple of questions I'd like to kindly ask is ---- what does "init" mean in the code below? Like, how come there are these really long underscores on each side of the word 'init'?
The other question is - what does the line "if name == "main": mean? I don't know where name came from, and also where main came from. Not only that.....they have underscores too.
Thanks in advance to all for helping me - to point me in the right direction in understanding this kind of coding style. It looks quite advanced, but at the same time amazes me how it created a GUI window that makes the square paddles move up and down independently.
Thanks all!!
'''Example that demonstrates keeping track of multiple key events'''
from tkinter import * #named tkinder in python 3, and capital Tkinter in python 2
class Playfield:
def __init__(self):
# this dict keeps track of keys that have been pressed but not
# released
self.pressed = {}
self._create_ui()
def start(self):
self._animate()
self.root.mainloop()
def _create_ui(self):
self.root = Tk()
self.p1label = Label(text="press w, s to move player 1 up, down",
anchor="w")
self.p2label = Label(text="press o, l to move player 2 up, down",
anchor="w")
self.canvas = Canvas(width=440, height=440)
self.canvas.config(scrollregion=(-20, -20, 420, 420))
self.p1label.pack(side="top", fill="x")
self.p2label.pack(side="top", fill="x")
self.canvas.pack(side="top", fill="both", expand="true")
self.p1 = Paddle(self.canvas, tag="p1", color="red", x=0, y=0)
self.p2 = Paddle(self.canvas, tag="p2", color="blue", x=400, y=0)
self._set_bindings()
def _animate(self):
if self.pressed["w"]: self.p1.move_up()
if self.pressed["s"]: self.p1.move_down()
if self.pressed["o"]: self.p2.move_up()
if self.pressed["l"]: self.p2.move_down()
self.p1.redraw()
self.p2.redraw()
self.root.after(10, self._animate)
def _set_bindings(self):
for char in ["w","s","o", "l"]:
self.root.bind("<KeyPress-%s>" % char, self._pressed)
self.root.bind("<KeyRelease-%s>" % char, self._released)
self.pressed[char] = False
def _pressed(self, event):
self.pressed[event.char] = True
def _released(self, event):
self.pressed[event.char] = False
class Paddle():
def __init__(self, canvas, tag, color="red", x=0, y=0):
self.canvas = canvas
self.tag = tag
self.x = x
self.y = y
self.color = color
self.redraw()
def move_up(self):
self.y = max(self.y -2, 0)
def move_down(self):
self.y = min(self.y + 2, 400)
def redraw(self):
x0 = self.x - 10
x1 = self.x + 10
y0 = self.y - 20
y1 = self.y + 20
self.canvas.delete(self.tag)
self.canvas.create_rectangle(x0,y0,x1,y1,tags=self.tag, fill=self.color)
if __name__ == "__main__":
p = Playfield()
p.start()