Can't modify a cross module variable - python-3.x

Question

I’m doing a home project with a raspi and a rain sensor.
Basically, with cronjobs, i run isitraining.py every 30 min.
If it is raining, i want it to increment a specific variable from another module (rains.water)
If it stops raining, i want it to decrease the same variable.
here are my codes:
rains.py
water=0
isitraining.py
import RPi.GPIO as GPIO
import rains
GPIO.setmode(GPIO.BCM)
GPIO.setup(4, GPIO.IN, pull_up_down=GPIO.PUD_UP)
def raincounter():
if (GPIO.input(4) and (0<rains.water<13)):
rains.water-=1 #No Rain
elif (GPIO.input(4)==0 and (0<rains.water<13)):
rains.water+=1 #Rain
testscript.py
import rains
import isitraining
isitraining.raincounter()
print (rains.water)
everytime i run the “testscript.py” for the first time, it does modify the “rains.water” variable but only one time, if i run the script any other time after that, it does not increment or decrease in value.
fyi
gpio.input(4) is a rain sensor with digital input. When it’s high, it means there’s no rain and when it’s low it means it is raining.
Any thoughts?

Answer 1

Every time testscript.py runs, it's importing isitraining.py fresh, from scratch, which then imports rains.py fresh, from scratch. rains.py and the water value it holds do not persist across runs.
If you want to save the value, you need to manually write it to disk, then load it later when you want to use it. Something like this:
isitraining.py:
import RPi.GPIO as GPIO
import rains
GPIO.setmode(GPIO.BCM)
GPIO.setup(4, GPIO.IN, pull_up_down=GPIO.PUD_UP)
def raincounter():
if (GPIO.input(4) and (0<rains.water<13)):
return rains.alter_rain(-1) #No Rain
elif (GPIO.input(4)==0 and (0<rains.water<13)):
return rains.alter_rain(1)
rains.py:
FILE_NAME = "rain_record.txt"
def alter_rain(n):
with open(FILE_NAME, "r") as f:
current_value = int(f.read()) # Get saved value
current_value += n # Alter it
with open(FILE_NAME, "w") as f:
f.write(str(current_value)) # Write the altered value back
return current_value # And return it so the caller knows the current value
testscript.py
import rains
import isitraining
new_val = isitraining.raincounter()
print (new_val)
You could combine the two calls to open, and should also include error handling, but this shows the general idea. You cannot use a simple script to act as a database for you like you're attempting to do. If you want to save something, you need to save it yourself.