How do end a function, see describe the problem for more deteils

I think you mean "Function Arguments", rather than "Argumentative Functions" - the latter doesn't exist and implies that the functions prefer to shout at each other rather than do anything useful! :laugh:

Function can have arguments, which are values that you can pass into the function for it to process, or they can have no arguments.
To declare a function with arguments, you write the list after the name:

def doubleIt(number)
   return number + number

And you can then call it with a different value each time:

print(doubleIt(2))
print(doubleIt(666))

If you don't want to pass any values to a function, then you leave the brackets empty:

def showMenu()
   print ("Press 1 for Sales")
   print ("Press 2 for Accounts")
   print ("Press 3 for the operator")
   print ("Press 0 to quit")

There are more details here: Python Functions (def): Definition with Examples[^] and here: Python Function Arguments (Default, Keyword and Arbitrary)[^]