仅当按下Python键时，才如何移动字符。

Question

I have been working through a book called python for kids. The last project in the book is about a platforming game. The game is called Mr Stick Man Races for the Exit. The way you move the character (a stickman) is you press left or right and he will move left or right. But unlike most games, if you let go of the key, he keeps moving. How do you make it so he will stop when the key is released?

Here is a link to a download of the code: https://www.nostarch.com/pythonforkids

If you press download sample code from the book, the program is "stickmangame7" in the chapter 18 folder. I have included this link in case I embedded the wrong bit on the code.

Here is some embedded code which may be the correct bit:

class StickFigureSprite(Sprite):
def __init__(self, game):
    Sprite.__init__(self, game)
    self.images_left = [
        PhotoImage(file="stick-L1.gif"),
        PhotoImage(file="stick-L2.gif"),
        PhotoImage(file="stick-L3.gif")
    ]
    self.images_right = [
        PhotoImage(file="stick-R1.gif"),
        PhotoImage(file="stick-R2.gif"),
        PhotoImage(file="stick-R3.gif")
    ]
    self.image = game.canvas.create_image(200, 470, image=self.images_left[0], anchor='nw')
    self.x = -2
    self.y = 0
    self.current_image = 0
    self.current_image_add = 1
    self.jump_count = 0
    self.last_time = time.time()
    self.coordinates = Coords()
    game.canvas.bind_all('<KeyPress-Left>', self.turn_left)
    game.canvas.bind_all('<KeyPress-Right>', self.turn_right)
    game.canvas.bind_all('<space>', self.jump)

Also:

 def turn_left(self, evt):
    if self.y == 0:
        self.x = -2

def turn_right(self, evt):
    if self.y == 0:
        self.x = 2

PS I know you can do this using pygame, but this is not using pygame for the rest, so I don't think that will work.

Answer 1

Without looking at the rest of the code, given that turn_left() and turn_right() methods are modifying self.x I would assume that in some event loop this value is used to calculate the movement of your 'stick' on the x axis. You probably want to reset it to 0 when a key gets released, so create an additional method for example:

def stop_movement(self, evt):
    self.x = 0

And when binding your KeyPress events, bind also KeyRelease events to that method, eg:

game.canvas.bind_all('<KeyRelease-Left>', self.stop_movement)
game.canvas.bind_all('<KeyRelease-Right>', self.stop_movement)