keyboard_trigger = Event() 返回“NameError：名称‘Event’未定义”

Question

背景：
我正在尝试为我的机器人编写一个简单的“物体避免”程序。

没有键盘中断事件的初始版本可以工作，但是当我尝试使用 CTL-C 退出时，程序停止，但机器人继续移动，直到我物理抓住它并将其关闭。

解决方案：
使用在不同程序中使用的技巧来侦听键盘事件，然后在检测到键盘事件时停止机器人。

代码：
有效代码的示例非常大（它是一个基于网络的 FPV 远程控制机器人），因此我没有逐字逐句地包含它，而是在 MediaFire 上包含了它的链接，因此这个问题不会成为长得难以忍受。 即：

https://www.mediafire.com/file/mzjr5s34sxy70yo/New_Remote_Camera_Robot.py/file

我

是有困难的代码（对象避免代码）要短得多，所以我已经将它逐字包含了。

# Object Avoidance Robot
# Drives in a straight line untill it reaches an obsticle within "X" cm.
# It then stops, backs up a few cm, turns a random amount, and then proceeds.

import easygopigo3 as easy
import time
import random
import signal
import os
import sys

gpg = easy.EasyGoPiGo3()
gpg = easy.EasyGoPiGo3()
servo_1 = gpg.init_servo('SERVO1')
servo_2 = gpg.init_servo('SERVO2')
sleep_time = 0.50  # pause time in seconds

my_distance_portI2C = gpg.init_distance_sensor('I2C')
time.sleep(0.1)

# for triggering the shutdown procedure when a signal is detected
keyboard_trigger = Event()
def signal_handler(signal, frame):
    print("Signal detected. Stopping threads.")
    gpg.stop()
    keyboard_trigger.set()

print("Running: Test Servos.\n")

# Read the connected robot's serial number
serial_number = gpg.get_id() # read and display the serial number

# For testing only - "invalid" serial number
# serial_number = "invalid"

print("This robot's serial number is\n"+serial_number+"\n")


# Servo constants for each robot

# Each robot is identified by its unique serial number

# Charlene:
if serial_number == "A0F6E45F4E514B4B41202020FF152B11":

# Charlene's servo constants
    print("Robot is \"Charlene\"")
    center_1 = 86  # Horizontal centering - smaller is further right.
    center_2 = 76  # Vertical centering - smaller is further up.

# Charlie:
elif serial_number == "64B61037514E343732202020FF111A05":

# Charlie's servo constants
    print("Robot is \"Charlie\"")
    center_1 = 86  # Horizontal centering - smaller is further right.
    center_2 = 90  # Vertical centering - smaller is further up.

else:
# Unknown serial number
    print("I don't know who robot", serial_number, "is,")
    print("If we got this far, it's obviously a GoPiGo robot")
    print("But I don't know what robot it is, so I'm using")
    print("the default centering constants of 90/90.\n")

# Default servo constants
    print("Robot is \"Unknown\"")
    print("Please record the robot's serial number, name,")
    print("and derived centering constants.")
    center_1 = 90
    center_2 = 90

# Start Test Servos

# Define excursions
right = center_1 - 45
left = center_1 + 45
up = center_2 - 45
down = center_2 + 45

def test_servos():
    # Test servos
    print("\nStarting test:")
    print("Using centering constants "+str(center_1)+"/"+str(center_2), "for this robot")

    print("\nCenter Both Servos")
    servo_1.rotate_servo(center_1)
    servo_2.rotate_servo(center_2)
    time.sleep(sleep_time)

    print("Test Servo 1 (horizontal motion)")
    servo_1.rotate_servo(right)
    time.sleep(sleep_time)
    servo_1.rotate_servo(left)
    time.sleep(sleep_time)
    servo_1.rotate_servo(center_1)
    time.sleep(sleep_time)

    print("Test Servo 2 (vertical motion)")
    servo_2.rotate_servo(up)
    time.sleep(sleep_time)
    servo_2.rotate_servo(down)
    time.sleep(sleep_time)

    print("Re-Center Both Servos")
    servo_1.rotate_servo(center_1)
    servo_2.rotate_servo(center_2)
    time.sleep(sleep_time)
    servo_1.disable_servo()
    servo_2.disable_servo()
    print("Complete: Test Servos - Exiting.")

def avoid():
    while True:
        while my_distance_portI2C.read_inches() > 20:
            gpg.forward()
            gpg.stop()
            time.sleep(1)
            gpg.backward()
            time.sleep(1)
            gpg.stop()
            test_servos()
            gpg.backward()
            time.sleep(4)
            gpg.stop()
            time.sleep(1)
            gpg.turn_degrees((random.randint(90, 270)), blocking=True)
            time.sleep(1) # slowdown


#------------------------------------
# Main routine entry point is here
#------------------------------------

if __name__ == "__main__":
    # registering both types of termination signals
    signal.signal(signal.SIGINT, signal_handler)
    signal.signal(signal.SIGTERM, signal_handler)

test_servos()  # make sure servos are centered
avoid()
logging.info("Finished!")
sys.exit(0)
while not keyboard_trigger.is_set():
    sleep(0.25)

# until some keyboard event is detected
print("\n ==========================\n\n")
print("A \"shutdown\" command event was received!\n")
gpg.stop()
exit()

问题： 当我在 VS Code 中运行 New_Remote_Camera_Robot.py 代码时，它可以工作。  （实际上，这不是因为机器人操作系统的这个特定安装尚未安装 nginx - 但它不会因

event

问题而失败。） 当我在 VS Code 中运行上面的 object_avoidance.py 代码时，它失败并显示：

pi@Charlene:~/Project_Files/object_avoidance $ /usr/bin/python /home/pi/Project_Files/object_avoidance/Object_Avoidence.py
Traceback (most recent call last):
  File "/home/pi/Project_Files/object_avoidance/Object_Avoidence.py", line 22, in <module>
    keyboard_trigger = Event()
NameError: name 'Event' is not defined
pi@Charlene:~/Project_Files/object_avoidance $

我绝对确定我错过了

某些东西

。  我同样确信这绝对是愚蠢的事情。 预先感谢您提供的任何帮助。

该错误是由于代码中未定义 Event 对象造成的。在Python中，Event对象来自线程模块，但似乎您还没有在Object_Avoidence.py脚本中导入它。

Answer 1