Continue python script even after error ocurred

Question

I have a Python script that logs temperature in my room and use requests library to send the data. Sometimes I lose wifi signal and the script stops completely after an error with the requests.

import sys
import time
import Adafruit_DHT
import requests

raspid = 1
sensor = 11
pin = 25

while True:   
    humidity, temperature = Adafruit_DHT.read_retry(sensor, pin)
    if humidity is not None and temperature is not None:
        datos = {'temperatura': 'temperature', 'humedad': 'humidity', 'raspid': 'raspid'}
        r = requests.post("http://httpbin.org/post", data=datos)
        print(r.text)
    else:
        print ('Error de lectura!')
        time.sleep(15)

Error when disconnected from wifi

Traceback (most recent call last):
  File "/home/pi/Desktop/dht11 request post.py", line 19, in <module>
    r = requests.post("http://mehr.cl/link.php", data=datos)
  File "/usr/lib/python2.7/dist-packages/requests/api.py", line 94, in post
    return request('post', url, data=data, json=json, **kwargs)
  File "/usr/lib/python2.7/dist-packages/requests/api.py", line 49, in request
    return session.request(method=method, url=url, **kwargs)
  File "/usr/lib/python2.7/dist-packages/requests/sessions.py", line 457, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/lib/python2.7/dist-packages/requests/sessions.py", line 569, in send
    r = adapter.send(request, **kwargs)
  File "/usr/lib/python2.7/dist-packages/requests/adapters.py", line 407, in send
    raise ConnectionError(err, request=request)
ConnectionError: ('Connection aborted.', error(101, 'Network is unreachable'))
>>> 

Is there a way to ignore the error and just try again?

Answer 1

Yes, there is. It's precisely trying, and catching any error raised.

Here is basically how it works:

try:
    # Some action that could raise an error

except:
    # What to do when an error occurs

For deeper explanation, check the documentation: Errors and Exceptions.

There are several built-in exceptions, among which, ConnectionError. If you know the exact exception you're expecting, then you must add it to the except clause:

try:
    # Actions that might raise a ConnectionError

except ConnectionError:
    # Process the error, for instance, try again

Answer 2

You may want to use a try-except statement. As follows

while True:
    try:
        #action which may create an error
    except Exception as exc:
        print('[!!!] {err}'.format(err=exc))
        #action to perform: Nothing in your case

Note that a good practice is that an error should never pass silently.

---

Following the discussion in comments, note also that if you use Exception to handle your error, you will still be able to stop the while-loop manually, since you use python27.