chained_list.py

#!/usr/bin/env python3
# coding: utf-8


class Node:
    def __init__(self, value, previous, next_):
        self.value = value
        self.previous = previous
        self.next = next_

    def __repr__(self):
        return str(self.value)


class ChainedList:
    def __init__(self, *args):
        self._first = None
        self._len = 0
        self._generate_list(args)

    def _generate_list(self, elements):
        self._len = len(elements)

        if len(elements) == 0:
            return
        elif len(elements) >= 1:
            self._first = Node(elements[0], None, None)
            e = self._first
            for i in range(1, len(elements)):
                e.next = Node(elements[i], e, None)
                e = e.next
            e.next = self._first
            self._first.previous = e

    def append(self, element):
        if self._first != None:
            last = self._first.previous
            new = Node(element, last, self._first)
            last.next = new
            self._first.previous = new
            self._len += 1
        else:
            self._generate_list([element])

    def insert(self, index, element):
        if self._first is None:
            self._generate_list([element])
        else:
            if index == 0:
                new = Node(element, self._first.previous, self._first)
                self._first = new
                self._first.next.previous = self._first
                self._first.previous.next = self._first
            else:
                i = 0
                e = self._first
                while i != index:
                    if e.next is not None:
                        e = e.next
                        i += 1
                    else:
                        break

                temp = Node(element, e.previous, e)

                e.previous = temp
                temp.previous.next = temp
                temp.next.previous = temp

            self._len += 1

    def __repr__(self):
        buffer = f"[{self._first}"
        e = self._first.next
        while e != self._first:
            buffer += f", {e}"
            e = e.next
        buffer += "]"
        return buffer

    def __len__(self):
        return self._len

    def __add__(self, other):
        if not isinstance(other, ChainedList):
            raise TypeError

        new = ChainedList()
        for element in self.iter():
            new.append(element)
        for element in other.iter():
            new.append(element)

        return new

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

        if self._first is None:
            raise IndexError

        if index < 0 or index >= len(self):
            raise IndexError

        if index == 0:
            return self._first.value

        i = 1

        e = self._first.next

        while i != index:
            e = e.next
            i += 1

        return e.value

    def __contains__(self, item):
        if self._first is None:
            return False

        if self._first.value == item:
            return True

        e = self._first.next
        while e != self._first:
            if e.value == item:
                return True
            e = e.next

        return False

    def iter(self):
        if self._first is not None:
            yield self._first
            e = self._first.next
            while e != self._first:
                yield e
                e = e.next

    def reverse_iter(self):
        if self._first is not None:
            yield self._first.previous
            e = self._first.previous.previous
            while e != self._first.previous:
                yield e
                e = e.previous


if __name__ == '__main__':
    c = ChainedList(1, 2, 3, 4)
    print(c)
    c.append(5)
    print(c)
    print(len(c))

    c.insert(0, 10)
    print(c)
    print(len(c))

    for e in c.iter():
        print(e, end=", ")
    print()

    for e in c.reverse_iter():
        print(e, end=", ")
    print()

    a = c + c
    print(c, a)

    print("10 in c", 10 in c)

    print(len(a))

    for i in range(len(c)):
        print(c[i])