I am trying to make a class that includes the ability to display the length of a list. However, I get the message 'List has 0 items' instead of the actual number.

Here is my code:

'''

```
    grocery_list = []
    class GroceryList:
        grocery_list = []
        def __init__(self):
            print('Grocery List Created')
        def add(self, item):
            self.grocery_list.append(item)
        def show(self):
    print(self.grocery_list)
        def size(self):
             print('List has {} items'.format(len(grocery_list)))

    gro_list = GroceryList()
    gro_list.add('Banana')
    gro_list.add('Cat Food')
    gro_list.show()
    gro_list.size()

```

'''

Any help is appreciated.