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Julez
Julez

Reputation: 1369

setting environment int variable in Linux for use in a while loop in python but loop doesn't stop

I'm controlling a LED on a raspberry pi 2 with Python. I want the LED to go on for x seconds. When I set an environment variable in Linux. For example, export t=5. The LED goes on but won't go off.

If I just set the variable in the python script everything works fine.

I'm setting an environment variable in Linux like so:

export t=5
sudo python test.py

And getting it in Python like so: 

 #!/usr/bin/env python

    import RPi.GPIO as GPIO
    import time
    import os


    GPIO.setmode(GPIO.BOARD)

    GPIO.setup(11,GPIO.IN, pull_up_down=GPIO.PUD_DOWN)

    GPIO.setup(12,GPIO.OUT)

    GPIO.output(12,0)

    s = 0

    t = os.environ.get('t')

    while s <= t:
            if (GPIO.input(11) == 1):

                            GPIO.output(12, 1)

                            time.sleep(0.1)

                            s += 0.1
            else:
                    GPIO.output(12, 0)

    GPIO.output(12, 0)

Upvotes: 2

Views: 1815

Answers (1)

jwodder
jwodder

Reputation: 57610

The values of environment variables — and thus the values of os.environ — are stored as strings. Thus, you need to convert t to a number in order for comparison with s to do what you want:

t = int(os.environ.get('t'))

Upvotes: 5

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