Custom List

from random import randint
from time import time

class Slot:
    def __init__ (self, data = None):
        self.data = data
        self.nslot = None #"Next slot". Links to the next slot

class cList:
    def __init__ (self):
        #Where iteration starts
        self.root = Slot()

        #The start is also the end of the container when it's empty
        self.tail = self.root

        self.csize = 0

    def get_slot (self, index):
        #Finds and returns the index'th slot
        if self.root is None: raise KeyError("List is empty")
        cslot = self.root #Current slot for iteration
        for n in range(index + 1):
            cslot = cslot.nslot #Advance cslot to its next linked slot
        if cslot is None: raise KeyError #Reached the end of the container
        return cslot

    def __getitem__ (self, key):
        return self.get_slot(key).data

    def __setitem__ (self, key, value):
        self.get_slot(key).data = value

    def add (self, data):
        #Mimics List's append()
        #Add a new slot linked to the container's tail
        self.tail.nslot = Slot(data)

        #Reassign the new tail of the container
        self.tail = self.tail.nslot

        #Increase the size counter by 1
        self.csize += 1

    def __iter__ (self):
        index = 0
        while True:
            try:
                yield self.__getitem__(index)
                index += 1
            except KeyError:
                raise StopIteration

    def __len__ (self):
        return self.csize

cl = cList()

cstime = time()
for n in range(1000000):
    cl.add(n)
cetime = time() - cstime
print("Custom list time:", cetime)
del cl

l = []

lstime = time()
for n in range(1000000):
    l.append(n)
etime = time() - lstime
print("List time:", etime)
del l