python class variable definition question

Cost is a local variable to money(), and is not accessible to result()

It's because the variables "cost" and "diners" aren't global variables (they're just local to the class). To have them as global variables you need to define as global variables, so your code should look something like this:

class calculator():
    def money(self):
        print("What was the cost?")
        global cost
        cost = int(input("> "))
        diners.amount_of_diners()

class diners():
    def amount_of_diners():
        print("How many people are with you?")
        global diners
        diners = int(input("> "))
        precent.precent_to_give()

class precent():
    def precent_to_give():
        print("How much '%' you want to give the waiter? ")
        #global prec #you can uncomment this to also include prec as a global variables if you want to do other equations with it as well
        prec = input("> ")
        result.the_end()

class result():
    def the_end():
        result = cost*diners
        print("The total amount of money each of you need have to give is: "+str(result))



calc = calculator()
calc.money()

There was also a problem with adding an int on to the string so I fixed that as well for you!

Another more efficient way of doing the same thing would be to use this code:

class calculator:
    cost=0
    def money(self):
        print("What was the cost?")
        calculator.cost = int(input("> "))
        diners.amount_of_diners()

class diners:
    diners=0
    def amount_of_diners():
        print("How many people are with you?")
        diners.diners = int(input("> "))
        precent.precent_to_give()

class precent:
    prec=0
    def precent_to_give():
        print("How much '%' you want to give the waiter? ")
        precent.prec = input("> ")
        result.the_end()

class result:
    def the_end():
        result = calculator.cost * diners.diners
        print("The total amount of money each of you need have to give is: "+str(result))



calc = calculator()
calc.money()

This works better since it still has each variable local to the class and just calls for the variable from the class outside the class; instead of having them all as global variables.

The print-statement in your result.the_end class-method is attempting to print the sum of two variables, neither of which have been defined within the scope of the function, or within a scope the function can see. The way your code is written, it looks as if you assume it should know about the variable cost from the calculator.money class-method, and the variable diners from the diners.amount_of_diners class-method.

That's not how this works. These variables are bound to the scope in which they were defined. There is no reason you should expect these variables to be visible in other classes.

The solution of course would involve making these variables visible in the result class by some means (passing arguments, global scope, etc). However, you really aren't using Python classes the way they're meant to be used - it looks to me like you're treating them like some kind of quasi-functions. That being said, the problem your program is trying to solve doesn't exactly necessitate classes in the first place - using simple functions would be more appropriate. If you insist on using classes for this problem, my first instinct tells me you shouldn't need more than one class to achieve the desired behavior. If I were you I would study some more. When I have a hard time coming up with an appropriate name for a class, or deciding on what kind of functionality it should expose, I write some pseudo-code that's meant to mimic the kind of code I wish I could write using my potential class.