StopIteration error with a generator in python

Question

The error asks for a StopIteration statement, which already exists and I may have just placed it in the wrong section of code. I can't find any use of a generator that is similar to this. The error:

Traceback (most recent call last):
  File "W:\My Data Sources\My Documents\A level\Computer Science\Python\Tasks\Painting estimate copy wout gen.py", line 102, in <module>
    area()
  File "W:\My Data Sources\My Documents\A level\Computer Science\Python\Tasks\Painting estimate copy wout gen.py", line 71, in area
    sub2()
  File "W:\My Data Sources\My Documents\A level\Computer Science\Python\Tasks\Painting estimate copy wout gen.py", line 48, in sub2
    area()
  File "W:\My Data Sources\My Documents\A level\Computer Science\Python\Tasks\Painting estimate copy wout gen.py", line 67, in area
    print("Please enter the dimensions of each wall in your",next(iter1),"when prompted.")
StopIteration

---

RoomDetails = []
wallDimensions = []
counter = 0


def rooms():


    RoomNum = str(input("Please enter the name of the room you require  painting (e.g. 'lounge'): "))

    RoomDetails.append(RoomNum)

    inp1 = input("Have you entered all the rooms you need to decorate? Y or N?: ")

    if inp1 == 'y':
    print("")


    elif inp1 == 'Y':
        print("")

    elif inp1 == 'n':
        print("These are the rooms you have entered thus far: ", RoomDetails)
        rooms()

    elif inp1 == 'N':
        print("These are the rooms you have entered thus far: ", RoomDetails)
        rooms()


def sub():

    wallH = float(input("What's the hieght of this wall? (In meters): "))
    wallW = float(input("What's the width of this wall? (In meters): "))

    wallD = wallH * wallW

    wallDimensions.append(wallD)


def sub2():

    global counter

    var3 = input("Have you entered the dimensions of all the walls in this room that require painting? Y or N?")
    if var3 == 'y':
        area()
    elif var3 == 'Y':
        area()
    elif var3 == 'n':
        sub()
        sub2()
    elif var3 == 'N':
        sub()
        sub2()


global iter1
iter1 = iter(RoomDetails)

def area():
    global counter
    counter = counter + 1


    print("Please enter the dimensions of each wall in your",next(iter1),"when prompted.")

   sub()

   sub2()

    if counter < len(RoomDetails):
        area()
    elif iter1 == RoomDetails[-1]:
        raise StopIteration



def calc():

    var4 = float
    var4 = sum(wallDimensions)
    #£4.24 per square metre for painting
   var5 = float
   var5 = 4.24
   finalAmount = var4 * var5
   print("The total cost to paint",RoomDetails,"will be £",finalAmount)
   input("...")



   print("Welcome to the evaluation")


   CustNum = input("Please enter your customer number: ")

   DateEst = input("Please enter the date of your estimate: ")

   rooms()

   area()

    calc()

Answer 1

You are comparing an iterator to a list element here:

iter1 == RoomDetails[-1]:

But the iterator won't 'be' the thing - it's more like a tool than a value. For example, an iterator of a list looks like this:

>>> iter([])
<listiterator object at 0x6ffffdaf090>

So unless your other object is the same iterator, it will always return False and so never raise the ValueError. Try making that test a little simpler and it should work.

Also, you haven't really created an iterator - you need to yield values to make your function a generator expression. It might be worth just returning a list or something simple to achieve your goal? Typically, an iterator would yield the return value of area():

if counter < len(RoomDetails):
    yield area()

And as you are simply calling area(), not iterating over it, you don't need it to be an iterator here anyway.