C-style Linked List Demo in Python

# Just for demo.  DON'T DO THIS IN PRODUCTION CODE

import sys

class List(object):
    class Node(object):
        def __init__(self, data):
            self.data = data
            self.next = None

    def __init__(self):
        self.head = None
        self.current = None

    def __iter__(self):
        while self.current is not None:
            yield self.current.data
            self.current = self.current.next
        self.current = self.head  # reset self.current for later use

    def __len__(self):
        count = 0
        while self.current is not None:
            count += 1
            self.current = self.current.next
        self.current = self.head  # reset self.current for later use
        return count

    def __getitem__(self, key):
        if not isinstance(key, int):
            raise TypeError

        value = None
        if key >= 0:
            count = 0
            while self.current is not None:
                if count == key:
                    value = self.current.data
                    break
                count += 1
                self.current = self.current.next

            self.current = self.head

            if key > count:
                raise IndexError
        else:
            count = -len(self)

            if key < count:
                raise IndexError

            while self.current is not None:
                if count == key:
                    value = self.current.data
                    break
                count += 1
                self.current = self.current.next

            self.current = self.head
        return value

    def __setitem__(self, key, value):
        if not isinstance(key, int):
            raise TypeError

        if key >= 0:
            count = 0
            while self.current is not None:
                if key == count:
                    self.current.data = value
                    break
                count += 1
                self.current = self.current.next
            self.current = self.head
            if key > count:
                raise IndexError
        else:
            count = -len(self)
            if key < count:
                raise IndexError
            while self.current is not None:
                if key == count:
                    self.current.data = value
                    break
                count += 1
                self.current = self.current.next
            self.current = self.head

    def append(self, data):
        klass = globals()[self.__class__.__name__]
        node = klass.Node(data)

        if self.head is None:
            self.head = node
            self.current = self.head
        else:
            current = self.head
            while current.next is not None:
                current = current.next
            current.next = node


if __name__ == '__main__':
    _list = List()
    _list.append(33)
    _list.append(55)
    _list.append(88)
    _list.append(77)

    print 'length:', len(_list)
    print '3rd item:', _list[2]
    print 'last item:', _list[-1]

    try:
        print _list[99]
    except IndexError:
        sys.stderr.write("Out of range\n")

    for e in _list:
        print e

    print 'Change _list item'
    _list[0] = 100
    for e in _list:
        print e

    try:
        _list[99] = 66
    except IndexError:
        sys.stderr.write("Out of range\n")

    for e in _list:
        print e