'MyClass' object has no attribute '__getitem__'

If you actually wanted to be able to access your attributes using inst["attr"] and to explain your error, you would need to add a __getitem__ to you class:

class MyClass(object):
    def __init__(self, id, a, b, c):
        self.myList     = []
        self.id         = id
        self.a          = a
        self.b          = b
        self.c          = c

    def addData(self, data):
        self.myList.append(data)

    def __getitem__(self, item):
        return getattr(self, item)

As others have noted, you can simply use

item.id

However, sometimes you do need to use this syntax if you are accessing a field dynamically:

item[dynamicField]

In that case, you can use the __getitem__() syntax as Anand suggested, however it is safer to use python's wrapper for __getitem__:

getattr(item, dynamicField)

item is not a dictionary but a class so it has different syntax for accessing members. Access id this way instead:

item.id