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python即使在处理异常时也会挂起

gpiozero raspberry-pi3 signals exception-handling python-3.x

Aryeh Gielchinsky · 技术社区 · 7 年前

我有一个树莓PI连接到MCP3008 ADC,它测量热敏电阻上的模拟电压。我正在使用 gpiozero 用于PI和ADC之间通信的python库。下面的代码运行了几分钟,然后抛出一个错误,然后挂起函数 get_temp_percent 。该函数返回ADC的五个测量值的平均值。我正在使用 Signal 在等待1秒后抛出异常以尝试通过挂起,但它只是抛出一个错误并挂起。看起来我的 except 正在读取语句。为什么我不能摆脱代码挂起?

import time
from gpiozero import MCP3008
from math import log
import pymysql.cursors
from datetime import datetime as dt
import signal 
import os


def handler(signum, frame):
    print('Signal handler called with signal', signum, frame)
    raise Exception("Something went wrong!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!")   


def get_temp_percent(pos=0):
    x=[]
    for i in range(0,5):
        while True:
            try:
                signal.signal(signal.SIGALRM, handler)
                signal.alarm(1)
                adc = MCP3008(pos)
                x.append(adc.value)
                #adc.close()
            except Exception as inst:
                print('get_temp_percent {}'.format(inst) )
                signal.alarm(0)
                continue
            break
        signal.alarm(0)
        time.sleep(.1)
    return round(sum(x)/len(x),5)


def write_date(temp0):
    <writes temp0 to mysql db >        

# Connect to the database
connection = pymysql.connect(host='', user='', password='', db='',cursorclass = pymysql.cursors.DictCursor)

while True:        
    temp_percent = get_temp_percent()
    print('Temp Percent = {}'.format(temp_percent) )

    <some function that do some arithmetic to go temp_percent to temp0>

    write_date(temp0)
    print('Data Written')

    time.sleep(1)
    print('Sleep time over')
    print('')

作用 get\u temp\u百分比 导致以下问题

Signal handler called with signal 14 <frame object at 0x76274800>
Exception ignored in: <bound method SharedMixin.__del__ of SPI(closed)>
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/gpiozero/mixins.py", line 137, in __del__
    super(SharedMixin, self).__del__()
  File "/usr/lib/python3/dist-packages/gpiozero/devices.py", line 122, in __del__
    self.close()
  File "/usr/lib/python3/dist-packages/gpiozero/devices.py", line 82, in close
    old_close()
  File "/usr/lib/python3/dist-packages/gpiozero/pins/local.py", line 102, in close
    self.pin_factory.release_all(self)
  File "/usr/lib/python3/dist-packages/gpiozero/pins/__init__.py", line 85, in release_all
    with self._res_lock:
  File "/home/pi/Desktop/testing exceptions.py", line 13, in handler
    raise Exception("Something went wrong!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!")
Exception: Something went wrong!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

1 回复 | 直到 7 年前

Hitobat 7 年前

看起来你对gpiozero的调用在幕后做了很多工作。在处理异常时,库正在尝试清理并卡住。

我快速查看了库的文档,看起来您可能可以保留这些别针,以便可以重复使用它们。

e、 g。

import ...

adcs = {}

def get_adc_value(pos):
    if pos not in adcs:
        adcs[pos] = MCP3008(pos)
    return adcs[pos].value

def get_temp_percent(pos=0):
    x = []
    for i in range(0, 5):
        x.append(get_adc_value(pos))
        time.sleep(.1)
    return round(sum(x)/len(x),5)

while True:
   temp_percent = get_temp_percent()
   ...