AttributeError：'NoneType'对象没有属性'group'

Question

请帮忙，因为我尝试使用树莓派Pir传感器将Pir传感器（为1或0）收集的数据传输到Web服务，但出现此错误

Traceback (most recent call last):
  File "pir_5.py", line 54, in <module>
    moveHold = float(matches.group(1))
AttributeError: 'NoneType' object has no attribute 'group'

这是我的代码

while True :

    # Read PIR state
    Current_State = GPIO.input(GPIO_PIR)

    if Current_State==1 and Previous_State==0:
      # PIR is triggered
      output =  subprocess.check_output(["echo", "18"]);
      print "  Motion detected!"
      # Tell the Pi to run our speech script and speak the words
      # motion dtected! - anything after the .sh will be read out.
      matches = re.search("Current_State==1 and Previous_State==0", output)
      moveHold = float(matches.group(1))
      resultm = client.service.retrieveMove(moveHold)

      cmd_string = './speech.sh motion detected!'
      # now run the command on the Pi.
      os.system(cmd_string)
      # Record previous state
      Previous_State=1
    elif Current_State==0 and Previous_State==1:
      # PIR has returned to ready state
      print "  Ready"
      Previous_State=0

    # Wait for 10 milliseconds
    time.sleep(0.01)

Answer 1

那么显然output中不包含预期的字符串。 （当通过调用echo 18生成它时，该怎么办？）

  matches = re.search("Current_State==1 and Previous_State==0", output)

返回None ，没有.group()

  moveHold = float(matches.group(1))

这样您就可以得到上述例外。

您应该将其更改为

    matches = re.search("Current_State==1 and Previous_State==0", output)
    if matches:
        moveHold = float(matches.group(1))
        resultm = client.service.retrieveMove(moveHold)
        ...
    else:
        # code for if it didn't match

Answer 2

在你写的那一点

matches.group(...)

比赛None 。 您的正则表达式搜索似乎找不到匹配项。 如果正则表达式搜索有可能失败，那么您需要显式处理该情况：

if matches is None:
    ....

也许真正的问题是执行搜索的代码是错误的。

除了让我确切地告诉您解决问题的方法外，您要学习的重点还在于如何解释此特定错误消息。