Check presence of a file

[Steffenwolt]

I followed killerex'es suggestion and made base.py

#!/bin/python

# baseprogram; calls the function status from key_check.py

import sys
import os
import time

from key_check import status

while True:
    
    on_or_off=status
    print (on_or_off)
    time.sleep(3)

and key_check.py that containes the function 'status'

#!/bin/python
 
#import RPi.GPIO as GPIO
import time
import os 

#GPIO.setup(22, GPIO.IN)

def status():
    foo = 5     # Lees de status van de GPIO pin uit.
    if (foo) == 4:
      #Schakelaar is AAN.
      key = 'ON'
    else:
      #Schakelaar is UIT.
      key = 'OFF'
    return (key)
      
datum = (time.strftime('%d/%m/%Y'))
#print(datum)
#keystat = status()
#print (keystat)

def _test():

   pass
 
if __name__ == '__main__':
    # This part runs only when this script is the main script, not when imported from other
    _test()

Running key_check on its own is OK.
When i call keycheck.status i get the following response:

Output:
Python 3.6.4
>>> %Run base.py
<function status at 0x037E4E40>
<function status at 0x037E4E40>
KeyboardInterrupt: Forced reset
>>> 

Any ideas about this?
As you will probably have noticed i am very much a novice, but i'll learn.
is there a site where i can learn about those situation?