声明类实例时的构造方法参数错误

Question

I was working on a class to control the power of two DC motors with the Raspberry Pi using the imported RPi.GPIO library. The code is as followed:

import RPi.GPIO as GPIO

class Motor:

    def _init_(self, MotorPin):
        self.MotorControlPin = MotorPin
        GPIO.setmode(GPIO.BOARD)
        GPIO.setup(self.MotorControlPin, GPIO.OUT)
        self.PWM = GPIO.PWM(self.MotorControlPin, 100)
    def SetPower(self, Power):
        self.PWM.start(Power)

When I try to create an instance of the class, RightMotor = Motor(12) Python returns the error Traceback (most recent call last): File "<pyshell#23>", line 1, in <module> RightMotor = Motor(12) TypeError: this constructor takes no arguments

The python IDLE seems to think that the _init_(self, Motor) function does not take any arguments. Am I using the function incorrectly? If not, what is the problem?

Answer 1

The name of the constructor method in Python is __init__ , with two underscores at the beginning and two at the end. Your code defines _init_ instead, which as far as Python is concerned is just another ordinary method with no bearing on object construction.