我可以在构造函数中创建线程吗?

Question

我有一个直流电机类。它的属性可以改变设定的旋转速度。为了控制实际速度，我想运行一个线程来保护加速度。因此，如果用户设置了一个新的速度，线程将慢慢提高实际速度以匹配设置的速度。我的方法:

import time
import threading
import RPi.GPIO as GPIO

class motorController:
#constructors
def __init__(self,maxPower,powerPin,directionPin,direction=True):
self.maxPower = abs(maxPower)
self.power = 0 #initially off
self.setPower = 0

#set pins motors are connected to
self.powerPin = powerPin
self.directionPin = directionPin
self.direction = direction

#initialize PWM
GPIO.setmode(GPIO.BCM)
#initialize powerPin
GPIO.setup(self.powerPin, GPIO.OUT) # set pin to output
self.powerPwm = GPIO.PWM(self.powerPin, 100)   # Initialize PWM on pwmPin 100Hz frequency, max is 8kHz, min is 10Hz
self.powerPwm.start(self.power) # Start PWM with 0% duty cycle

#initialize directionPin
GPIO.setup(self.directionPin, GPIO.OUT,initial=self.direction) # set pin to output

#initialize controll deamon
self.__lastCall = time.time()
self.setPointIsNotReached = threading.Condition() #currently unused
self.deamonTimeLock = threading.Lock()
self.controllThread = threading.Thread(target=self.__powerControllerDeamon())
self.controllThread.setDaemon(True)
self.controllThread.start()

def setTargetPower(self,setPower):
setPower = min(setPower,self.maxPower)
self.setPower = max(setPower,-self.maxPower)
with self.deamonTimeLock:
self.__lastDeamonCall = t
def __setPower(self,power):
#limit power to maxPower
self.power = min(abs(power),self.maxPower)
self.powerPwm.ChangeDutyCycle(self.power)
#set rotation direction
if power < 0:
self.direction = False
else:
self.direction = True
GPIO.output(self.directionPin, self.direction) #set to 3.3V if direction is true, or 0V if direction is false
def __powerControllerDeamon(self):
#private method that controls the power of the motor
t = time.time()
dt = t-self.__lastCall

if self.power > self.setPower:
m = -50 #ramp from 100 to 0 in minimal 2 sec
else:
m = 20 # ramp from 0 to 100 in minimal 5sec

newPower = self.power + m * dt
#detect if power is reched through change of sign
dP = self.setPower - self.power
dP2 = self.setPower - newPower
if dP*dP2 <= 0: #change of sign or one is zero
newPower = self.setPower #set point reached
else:
with self.setPointIsNotReached
self.setPointIsNotReached.notify()#set point NOT reached
print(newPower)
self.__setPower(newPower)
with self.deamonTimeLock:
self.__lastDeamonCall = t

和

from motorController import motorController as mC
import time
try:
m1 = mC(100,18,17)
m1.setTargetPower(100)
time.sleep(10) #should have powered up by now
except BaseException as e:
import RPi.GPIO as GPIO
GPIO.cleanup()
raise(e)

在这个例子中，线程函数被调用一次，然后不再调用。

我是线程和python的新手。我的问题:

1. 我可以从构造函数创建一个线程，并让它运行，直到主程序结束(这就是为什么我设置daemon为真)?
2. 如果答案是肯定的，我错在哪里?

Answer 1

你的__powerControllerDeamon方法应该包含一个循环，直到它达到所需的速度或直到它被告知停止。

由于它不包含循环，因此它将运行一次并退出。

注意，这个循环还应该包含少量的sleep，以防止它占用CPU。