Python中的事件驱动编程：更改颜色&；乌龟的大小

我的任务是用乌龟画一个红绿灯。每次我撞到太空，乌龟都会以不同的颜色移动，交通灯也会改变。我已经成功地完成了这项任务。但还有一些额外的任务我无法完成

1） 用R、G和B改变海龟的颜色。例如：海龟处于绿灯（底部）位置。但我想按R把它改成红色

2） 我想用+和-，改变我海龟的养老金

这是我的代码。我就是写不出额外的行来完成这两项任务

import turtle           # Tess becomes a traffic light.

turtle.setup(400,500)
wn = turtle.Screen()
wn.title("Tess becomes a traffic light!")
wn.bgcolor("lightgreen")
tess = turtle.Turtle()


def draw_housing():
    """ Draw a nice housing to hold the traffic lights """
    tess.pensize(3)
    tess.color("black", "darkgrey")
    tess.begin_fill()
    tess.forward(80)
    tess.left(90)
    tess.forward(200)
    tess.circle(40, 180)
    tess.forward(200)
    tess.left(90)
    tess.end_fill()


draw_housing()

tess.penup()
# Position tess onto the place where the green light should be
tess.forward(40)
tess.left(90)
tess.forward(50)
# Turn tess into a big green circle
tess.shape("circle")
tess.shapesize(3)
tess.fillcolor("green")

# A traffic light is a kind of state machine with three states,
# Green, Orange, Red.  We number these states  0, 1, 2
# When the machine changes state, we change tess' position and
# her fillcolor.

# This variable holds the current state of the machine
state_num = 0





def advance_state_machine():
    global state_num



    if state_num == 0:       # Transition from state 0 to state 1
        tess.forward(70)
        tess.fillcolor("orange")
        state_num = 1
    elif state_num == 1:     # Transition from state 1 to state 2
        tess.forward(70)
        tess.fillcolor("red")
        state_num = 2
    else:                    # Transition from state 2 to state 0
        tess.back(140)
        tess.fillcolor("green")
        state_num = 0

# Bind the event handler to the space key.
wn.onkey(advance_state_machine, "space")

wn.listen()                      # Listen for events
wn.mainloop()

---

我对您的需求的解释与@avalanche不同——我的解决方案如下。这一切仍然取决于添加更多的关键事件（比如你的空格键事件），正如@avalanche为他展示的so+1：

""" Tess becomes a traffic light. """

from turtle import Turtle, Screen

def draw_housing():
    """ Draw a nice housing to hold the traffic lights """
    tess.pensize(3)
    tess.color('black', 'darkgrey')

    tess.begin_fill()
    tess.forward(80)
    tess.left(90)
    tess.forward(200)
    tess.circle(40, 180)
    tess.forward(200)
    tess.end_fill()

wn = Screen()
wn.setup(400, 500)
wn.title("Tess becomes a traffic light!")
wn.bgcolor('lightgreen')

tess = Turtle()

draw_housing()

# Position tess onto the place where the green light should be
tess.penup()
tess.left(90)
tess.forward(40)
tess.left(90)
tess.forward(50)

# Turn tess into a green circle
tess.shape('circle')
tess.shapesize(3)
tess.fillcolor('green')

# A traffic light is a kind of state machine with three states,
# Green, Amber, Red.  We number these states  0, 1, 2
# When the machine changes state, we change tess' position and
# her fillcolor.

SLOW, STOP, GO = range(3)

# Y position, color, next state; 'orange' filling in for 'amber'
STATE_MACHINE = { \
    SLOW: (120, 'orange', STOP), \
    STOP: (190, 'red', GO), \
    GO: (50, 'green', SLOW) \
}

# This variable holds the current state of the machine
state_num = SLOW

def advance_state_machine():
    global state_num

    position, color, next_state = STATE_MACHINE[state_num]

    tess.sety(position)
    tess.fillcolor(color)
    state_num = next_state

def bigger():
    stretch_wid, stretch_len, outline = tess.shapesize()
    tess.shapesize(stretch_wid, stretch_len, outline + 1)

def smaller():
    stretch_wid, stretch_len, outline = tess.shapesize()
    if outline > 0:
        tess.shapesize(stretch_wid, stretch_len, outline - 1)

def stop():
    global state_num
    state_num = STOP
    advance_state_machine()

def slow():
    global state_num
    state_num = SLOW
    advance_state_machine()

def go():
    global state_num
    state_num = GO
    advance_state_machine()

# Bind the event handlers
wn.onkey(advance_state_machine, 'space')
wn.onkey(stop, 'r')  # press 'r' key to change the light to red
wn.onkey(slow, 'y')  # press 'y' key to change the light to yellow
wn.onkey(go, 'g')  # press 'g' key to change the light to green
wn.onkey(bigger, 'plus')  # press '+' key to increase the circle size
wn.onkey(smaller, 'minus')  # press '-' key to decrease the circle size.

wn.listen()  # Listen for events

wn.mainloop()

一个区别是“r”、“y”和“g”键将灯光推进到该颜色状态，而不仅仅是更改当前光标的颜色。“+”和“-”键改变的是画笔轮廓的大小，而不是光标的大小

此外，我还修改了状态机逻辑和其他细节。

我发现“-”（和“+”）在Tk键绑定方面有特殊意义，所以请尝试使用

wn.onkey（较小的“减”）

（和

wn.onkey（较大的“加”）

）。

""" Tess becomes a traffic light. """

from turtle import Turtle, Screen

def draw_housing():
    """ Draw a nice housing to hold the traffic lights """
    tess.pensize(3)
    tess.color('black', 'darkgrey')

    tess.begin_fill()
    tess.forward(80)
    tess.left(90)
    tess.forward(200)
    tess.circle(40, 180)
    tess.forward(200)
    tess.end_fill()

wn = Screen()
wn.setup(400, 500)
wn.title("Tess becomes a traffic light!")
wn.bgcolor('lightgreen')

tess = Turtle()

draw_housing()

# Position tess onto the place where the green light should be
tess.penup()
tess.left(90)
tess.forward(40)
tess.left(90)
tess.forward(50)

# Turn tess into a green circle
tess.shape('circle')
tess.shapesize(3)
tess.fillcolor('green')

# A traffic light is a kind of state machine with three states,
# Green, Amber, Red.  We number these states  0, 1, 2
# When the machine changes state, we change tess' position and
# her fillcolor.

SLOW, STOP, GO = range(3)

# Y position, color, next state; 'orange' filling in for 'amber'
STATE_MACHINE = { \
    SLOW: (120, 'orange', STOP), \
    STOP: (190, 'red', GO), \
    GO: (50, 'green', SLOW) \
}

# This variable holds the current state of the machine
state_num = SLOW

def advance_state_machine():
    global state_num

    position, color, next_state = STATE_MACHINE[state_num]

    tess.sety(position)
    tess.fillcolor(color)
    state_num = next_state

def bigger():
    stretch_wid, stretch_len, outline = tess.shapesize()
    tess.shapesize(stretch_wid, stretch_len, outline + 1)

def smaller():
    stretch_wid, stretch_len, outline = tess.shapesize()
    if outline > 0:
        tess.shapesize(stretch_wid, stretch_len, outline - 1)

def stop():
    global state_num
    state_num = STOP
    advance_state_machine()

def slow():
    global state_num
    state_num = SLOW
    advance_state_machine()

def go():
    global state_num
    state_num = GO
    advance_state_machine()

# Bind the event handlers
wn.onkey(advance_state_machine, 'space')
wn.onkey(stop, 'r')  # press 'r' key to change the light to red
wn.onkey(slow, 'y')  # press 'y' key to change the light to yellow
wn.onkey(go, 'g')  # press 'g' key to change the light to green
wn.onkey(bigger, 'plus')  # press '+' key to increase the circle size
wn.onkey(smaller, 'minus')  # press '-' key to decrease the circle size.

wn.listen()  # Listen for events

wn.mainloop()