Issue Calling Method Outside Class Python

I'm working on a python assingment involving creating and using a class with several methods. I won't post the whole thing as it'll be simpler to point out my issue if I instead sh

Solution 1:

Basically you are calling an instance method without an instance that's why you are getting this error

    TypeError: unbound method return_list() must be calledwith Fruit instance asfirst argument (got int instance instead)

The corrected code

    fruit_1.return_list(fruit_choice)

The way you are doing is the behaviour of static methods, they are called without an instance. Please go through some oops programming like instance methods and static methods in python.

Hope it helps :)

Solution 2:

You seem to have a misunderstanding of Classes and class instances.

The return_list function you have defined is part of the Fruit class, i.e. each instance of the Fruit class contains this method. But the use of this function, which is to return a specific fruit from fruit list, is independent of the individual Fruit instances, which means this method should not have been in the Fruit class in the first place.

The signature of class definition class Fruit(self,color,name) is wrong. It should be class Fruit:. The initial parameters should be defined as parameters to the __init__ method.

The list fruit_list should contain Fruit instances. The program could be written as:

classFruit:
    def__init__(self, color, name):
        self.color = color
        self.name = name

    def__str__(self):
        return'I am a ' + self.color + ' ' + self.name

fruit_list = []

fruit_1 = Fruit("red", "apple")
fruit_list.append(fruit_1)

fruit_choice = int(raw_input("What fruit would you like?"))
print(fruit_list[fruit_choice])

Printing a Python object calls the __str__ magic method.

If you do really want to have a separate function which returns a Fruit from the fruit_list, you can define a function outside the class (but these seem unnecessary when you can directly access the instance using the index):

def return_list(list, index):
    return list[index]

or

defreturn_list(index):
    global fruit_list
    return fruit_list[index]

If you try to print the entire list using print(fruit_list) the output is:

[<__main__.Fruit instance at 0x110091cf8>]

That is because Python does not call __str__ on each instance when you print a list of instances. You can print the fruit_list by doing:

for fruit in fruit_list:
    print(fruit)

Solution 3:

Here's a possible solution to your problem:

classFruit():

    def__init__(self, color, name):
        self.color = color
        self.name = name

    def__str__(self):
        return"Color: {0} Name: {1}".format(self.color, self.name)


classFruitBasket():

    def__init__(self):
        self.fruits = []

    defget_fruit(self, index):
        try:
            value = self.fruits[index]
            return value
        except Exception as e:
            print"Error with index {0} -> {1}".format(index, e)

if __name__ == "__main__":
    basket = FruitBasket()
    names = ["apple", "orange", "lemon"]
    colors = ["green", "orange", "yellow"]

    for name, color inzip(names, colors):
        fruit = Fruit(color, name)
        basket.fruits.append(fruit)

    print basket.get_fruit(0)
    print basket.get_fruit(1)
    print basket.get_fruit(2)
    basket.get_fruit(3)

Few comments about the above code:

• Fruit object doesn't have more responsabilities than setting up a fruit with a certain name & color, that's pretty much. One fruit shouldn't contain any list of fruits, that should be the responsability of another object
• FruitBasket is the container of fruits, you could do perfectly this without using OOP but for the sake of this question, this is a valid option to hold many fruits

With respect to your error, the other answers and comments are already pointing out what's wrong. Also, about class Fruit(self,color,name):, don't do that, in that sentence you're declaring the class type, not the constructor.

I'd strongly recommend you try to follow some of the many OOP python tutorials out there.