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I am using PIGPIO library to read temperature and humidity from a DHT22 sensor. This is the script I am using.

import os
import sys
import time
import pigpio
pi = pigpio.pi()
import DHT22
s = DHT22.sensor(pi,4,17)
s.trigger()
time.sleep(0.2)
print("{} {} {:3.2f} {} {} {} {}".format(
    s.humidity(), s.temperature(), s.staleness(),
    s.bad_checksum(), s.short_message(), s.missing_message(),
    s.sensor_resets()))
s.cancel()
pi.stop()

the script runs well and return the temperature and humidity as expected. However, in my terminal I got the following error:

Error in atexit._run_exitfuncs:
Traceback (most recent call last):
  File "/usr/lib/python2.7/atexit.py", line 24, in _run_exitfuncs
    func(*targs, **kargs)
  File "/home/pi/share/dht_py/pigpio_dht22/DHT22.py", line 238, in cancel
    self.pi.set_watchdog(self.gpio, 0)
  File "/usr/local/lib/python2.7/dist-packages/pigpio.py", line 1764, in set_watchdog
    self.sl, _PI_CMD_WDOG, user_gpio, int(wdog_timeout)))
  File "/usr/local/lib/python2.7/dist-packages/pigpio.py", line 983, in _pigpio_command
    sl.s.send(struct.pack('IIII', cmd, p1, p2, 0))
AttributeError: 'NoneType' object has no attribute 'send'
Error in sys.exitfunc:
Traceback (most recent call last):
  File "/usr/lib/python2.7/atexit.py", line 24, in _run_exitfuncs
    func(*targs, **kargs)
  File "/home/pi/share/dht_py/pigpio_dht22/DHT22.py", line 238, in cancel
    self.pi.set_watchdog(self.gpio, 0)
  File "/usr/local/lib/python2.7/dist-packages/pigpio.py", line 1764, in set_watchdog
    self.sl, _PI_CMD_WDOG, user_gpio, int(wdog_timeout)))
  File "/usr/local/lib/python2.7/dist-packages/pigpio.py", line 983, in _pigpio_command
    sl.s.send(struct.pack('IIII', cmd, p1, p2, 0))
AttributeError: 'NoneType' object has no attribute 'send'

What is the cause of this error and how to avoid that? Thank you in advance.

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1

Odd. It looks like the connection to the Pi has been terminated by the pi.stop() before s.cancel() has completed all it needed to do in the background.

I'd try adding a time.sleep(0.2) after the s.cancel() to see if that gets around the problem.

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2
  • thank you for your answer. I added the time.sleep(0.2) but unfortunately I still got the error. I also try to execute the script line by line in the terminal instead of executing a script file. The error appeared after I execute the exit() command after pi.stop().
    – Leonard AB
    Dec 28 '17 at 5:29
  • I think this post is relevant github.com/joan2937/pigpio/issues/16 . My question now is, should I remove the atexit import and atexit call on the DHT22.py? is that safe?
    – Leonard AB
    Dec 28 '17 at 5:42

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