local variable 'count' defined in enclosing scope on line 10 referenced before assignment

Question

I am having an issue with the following code of Python 3 (the line at 5th position from bottom count=count+1):

import base64
import json
from google.cloud import iot_v1
import os
from twilio.rest import Client

account_sid = os.environ['TWILIO_ACCOUNT_SID']
auth_token = os.environ['TWILIO_AUTH_TOKEN']
client = Client(account_sid, auth_token)
count = 0


def device_config(config):
    client = iot_v1.DeviceManagerClient()
    name = client.device_path(<project_ID>,
                              <Region>,  <Registry>, <Device_ID>)
    binary_data = bytes(config, 'utf-8')
    client.modify_cloud_to_device_config(name, binary_data)


def hello_pubsub(event, context):
    if 'data' in event:
        data = event['data']
        data = base64.b64decode(data)
        data = data.decode('utf-8')
        data = json.loads(data)

        temperature = float(data['temperature'])

        if temperature > 25.0:
            device_config("ledon")
            if count < 1:
                client.calls.create( \
                    url=<URL>,
                    to=os.environ['TWILIO_TO'],
                    from_=os.environ['TWILIO_FROM'])
                count = count+1
        else:
            device_config("ledoff")
    else:
        print("Data is not present!")

This function will be called continuously (imagine like an infinite loop will call this function). I want to update count by 1 when first time temperature goes above 25 and for later calls, how high it may go, LED should be on, but calling shouldnot be done

You need to add `global count` on the first line of the `hello_pubsub` function. — grooveplex, Aug 06 '19 at 14:16

hiro protagonist · Accepted Answer · 2019-08-06T14:19:39.067

8

in hello_pubsub(event, context) you assign to count in the line count = count+1. which makes python look for count in the function scope (where it has not been defined and therefore lookup on the right-hand-side [count+1] fails).

this might be a worhty read: https://python-textbok.readthedocs.io/en/1.0/Variables_and_Scope.html#variable-scope-and-lifetime

you need to tell python that you mean the global count:

def hello_pubsub(event, context):
    global count
    ...

probably cleaner would be:

def hello_pubsub(count, event, context):
    ...

and then call it using:

hello_pubsub(count, event, context)

edited Aug 06 '19 at 14:19

answered Aug 06 '19 at 14:16

hiro protagonist

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I wouldn't encourage using globals – clubby789 Aug 06 '19 at 14:17
@JammyDodger neither would i (in general). but this explains the error and would fix the problem. – hiro protagonist Aug 06 '19 at 14:18

score 1 · Answer 2 · answered Aug 06 '19 at 14:15

1

You are referencing count inside a function, whereas it is defined outside. You should pass count as a parameter.

answered Aug 06 '19 at 14:15

clubby789

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would it work if they were to make it a global variable – oroy Aug 06 '19 at 14:16
Sorry, but why are globals so bad? – oroy Aug 06 '19 at 14:16
https://stackoverflow.com/questions/19158339/why-are-global-variables-evil – clubby789 Aug 06 '19 at 14:17

score 1 · Answer 3 · answered Aug 06 '19 at 14:17

1

You should pass count into the function as a parameter, and increment it in the loop that will call the function. If you absolutely need to assign to it within the function, you can use the statement global count before you do the assignment.

answered Aug 06 '19 at 14:17

Rob Streeting

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score 1 · Answer 4 · answered Aug 06 '19 at 14:35

You are trying to call a local variable into another function. You also need to pass the variable into the function. Hope this helps!

account_sid = os.environ['TWILIO_ACCOUNT_SID']
auth_token = os.environ['TWILIO_AUTH_TOKEN']
client = Client(account_sid, auth_token)
global count = 0



def hello_pubsub(event, context,count):

local variable 'count' defined in enclosing scope on line 10 referenced before assignment

4 Answers4