python - 处理多个IO错误

Question

我有几个在类init上执行的IO操作，但它们通常会因IOError而失败。我想做的是延迟几百毫秒，然后重试直到成功或某个定义的超时。在继续/结束循环之前，如何确保每个单独的命令成功执行？我认为有一种比对每个项目使用if语句和检查所有命令是否成功的计数器更好的方法。

我下面的当前代码通常会因IOError失败而挂起应用程序的其余部分。

   def __init__(self):
      print("Pressure init.")
      self.readCoefficients()

   def readCoefficients(self):
      global a0_MSB;
      global a0_LSB;
      global b1_MSB;
      global b1_LSB;
      global b2_MSB;
      global b2_LSB;
      global c12_MSB;
      global c12_LSB;

      a0_MSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_A0_COEFF_MSB+0);
      a0_LSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_A0_COEFF_LSB+0);

      b1_MSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_B1_COEFF_MSB+0);
      b1_LSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_B1_COEFF_LSB+0);

      b2_MSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_B2_COEFF_MSB+0);
      b2_LSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_B2_COEFF_LSB+0);

      c12_MSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_C12_COEFF_MSB+0);
      c12_LSB = Pressure.bus.read_byte_data(Pressure.MPL115A2_ADDRESS,Pressure.MPL115A2_REGISTER_C12_COEFF_LSB+0);

Answer 1

如果可以依次读取所有文件，则可以使用一个简单的功能。

import time

# ...

def readCoefficients(self):
    global a0_MSB;
    global a0_LSB;
    global b1_MSB;
    global b1_LSB;
    global b2_MSB;
    global b2_LSB;
    global c12_MSB;
    global c12_LSB;

    max_retries = 15

    a0_MSB = self.readretry(Pressure.MPL115A2_REGISTER_A0_COEFF_MSB+0, max_retries)
    a0_LSB = self.readretry(Pressure.MPL115A2_REGISTER_A0_COEFF_LSB+0, max_retries)

    b1_MSB = self.readretry(Pressure.MPL115A2_REGISTER_B1_COEFF_MSB+0, max_retries)
    b1_LSB = self.readretry(Pressure.MPL115A2_REGISTER_B1_COEFF_LSB+0, max_retries)

    b2_MSB = self.readretry(Pressure.MPL115A2_REGISTER_B2_COEFF_MSB+0, max_retries)
    b2_LSB = self.readretry(Pressure.MPL115A2_REGISTER_B2_COEFF_LSB+0, max_retries)

    c12_MSB = self.readretry(Pressure.MPL115A2_REGISTER_C12_COEFF_MSB+0, max_retries)
    c12_LSB = self.readretry(Pressure.MPL115A2_REGISTER_C12_COEFF_LSB+0, max_retries)

    def readretry(self, address, max_retries):
        for i in range(max_retries):
            try:
                return Pressure.bus.read_byte_data(
                    Pressure.MPL115A2_ADDRESS,
                    address
                )
            except IOError as e:
                # print(e)
                time.sleep(0.1)
        else:
            raise IOError("Reading failed after multiple tries")

注意:请勿使用全局变量，尤其是在类中。