linkedlist-ap4002/linkedlist.py

from typing import Union, Any
from dataclasses import dataclass


class ListIsEmpty(Exception):
    pass


@dataclass
class Node:
    value: Any
    next_: Any


class LinkedList:
    def __init__(self):
        self.__head: Union[None, Node] = None
    
    def __getitem__(self, n: int) -> Any:
        if self.__head is None:
            raise ListIsEmpty()
        i = 0
        ptr = self.__head
        while i < n:
            if ptr.next_ is None:
                raise IndexError()
            i += 1
            ptr = ptr.next_
        return ptr.value

    def __setitem__(self, n: int, value: Any):
        ptr = self.__head
        for i in range(n):
            ptr = ptr.next_
            print(f"At {i}")
        ptr.value = value

    def index(self, value: Any) -> int:
        ptr = self.__head
        i = 0
        while True:
            if ptr.value == value:
                return i
            else:
                i += 1
                ptr = ptr.next_
            if ptr is None:
                break
        raise ValueError()

    def append(self, value: Any):
        ptr = self.__head
        if ptr is None:
            self.__head = Node(value=value, next_=None)
            return
        while True:
            if ptr.next_ is None:
                break
            ptr = ptr.next_
        ptr.next_ = Node(value, next_=None)

    def prepend(self, value: Any):
        new_node = Node(value=value, next_=self.__head)
        self.__head = new_node