Question

I’m trying to make a very simple calculator in python. I’ve made a working one before using only functions, but adding classes is proving to be hard.

def askuser():
    global Question, x, y

    Question = input("""Enter a word: ("Add", "Subtract", "Multiply", "Divise")""")
    x = int(input("Enter first number: "))
    y = int(input("Enter second number: "))

class calculating:

    def __init__(self, x, y):
        self.x = x
        self.y = y

    def add(self):
        return self.x + self.y

    def subtract(self):
        return self.x - self.y

    def multiplication(self):
        return self.x * self.y

    def division(self):
        return self.x / self.y

math = calculating

def calc():

    if Question == "Add":
        t = math.add
        print(t)

    elif Question == "Subtract":
        t = math.subtract
        print(t)

    elif Question == "Multiply":
        t = math.multiplication
        print(t)

    elif Question == "Division":
        t = math.division
        print(t)

def final():
    input("Press any key to exit:" )


def main():

    askuser()
    calc()
    final()

main()

Code runs fine but it gives me an “error” instead of outputting a calculation:

   Enter a word: ("Add", "Subtract", "Multiply", "Divise")Add

   Enter first number: 5

   Enter second number: 5

   function add at 0x02E4EC90

   Press any key to exit:

Why would that be? Any help would be great, thanks.

Answer 1

You are printing the function itself, not the result of calling it. Try:

def calc():

if Question == "Add":
    t = math.add

elif Question == "Subtract":
    t = math.subtract

elif Question == "Multiply":
    t = math.multiplication

elif Question == "Division":
    t = math.division

print t()

Or cleaner but more advanced:

class UserInputCalculator(object):

    operations = ["Add", "Subtract", "Multiply", "Divide"]

    def __init__(self):
        self.x = None
        self.y = None
        self.operation = None

    def run(self):
        self.prompt_for_operation()
        self.prompt_for_x()
        self.prompt_for_y()
        if self.operation == 'Add':
            return self.add()
        elif self.operation == 'Subtract':
            return self.subtract()
        elif self.operation == 'Multiply':
            return self.multiply()
        elif self.operation = 'Divide':
            return self.divide()
        else:
            raise ValueError('Unknown operation %s.' % operation)

    def prompt_for_operation(self):
        self.operation = input("Enter an operation: (%s)" % ', '.join(UserInputCalculator.operations))
        if self.operation not in UserInputCalculator.operations:
            raise ValueError('%s not a valid operation.' % self.operation)
        return self.operation

    def prompt_for_x(self):
        try:
            self.x = int(input("Enter first number: "))
        except:
            raise ValueError('Invalid value.')
        return self.x

    def prompt_for_y(self):
        try:
            self.y = int(input("Enter second number: "))
        except:
            raise ValueError('Invalid value.')
        return self.y

    def add(self):
        return self.x + self.y

    def subtract(self):
        return self.x - self.y

    def multiply(self):
        return self.x * self.y

    def divide(self):
        return self.x / self.y

calculator = UserInputCalculator()
print calculator.run()
input("Press any key to exit:" )