Week 8

Lecture

Hi everyone!

So this week’s lectures were based on learning about the Linked List class. This class is pretty similar to a nested list, except the LinkedLists have a first parameter as an item, and the second as a LinkedList. Here is an example of the class LinkedList:

class LinkedList:

    """Linked list class"""

    def __init__(self: 'LinkedList', item: object=None,

                 rest: 'LinkedList'=None) -> None:

        """Create a new LinkedList

        item - The first element of the linked list,

        Not present if self will be the empty linked list.

        rest - The linked list that contains the elements after item.

        Not present if self will be the empty linked list."""

        self.empty = (item is None) and (rest is None)

        if not self.empty:

            self.item = item

            if rest is None:

                self.rest = LinkedList()

            else:

                self.rest = rest

As the description says, the first item in the LinkedList is either a value, or it’s empty, and “rest” is either a LinkedList or empty. Some methods that we’ve created for the class LinkedList include:

Prepend (Put an item at the front of the list, and move the previous first item into “rest”)

__repr__(Returns a string representation of LinkedList)

Decapitate (Delete the first item in the LinkedList)

This week we learnt how to implement some of these methods in the LinkedList class, for example:

def prepend(self: 'LinkedList', head: object) -> None:

old_head = copy(self)

self.rest = old_head

self.head = head

self.empty = False

We also learnt how to implement other methods, such as insertion and deletion, basically how to add and remove values from the LinkedList. Luckily, I found it pretty easy to understand since it’s similar to how nested lists work, and the recursive functions we’d have to write would be similar to nested list functions.

Lab 7

In this week’s lab, we had to implement a few methods into the LinkedList class such as:

__len__

__setitem__

__delitem__

insert

After last week’s lab where we had to write our old class Queue and it’s methods by using LinkedList methods, this week’s lab seemed a lot easier since I now had a better understanding of LinkedList and how it’s methods worked. Although we had to use a lot of recursion to implement these methods, my partner and I ended up completing this lab without too much difficulty.

Assignment 2 Part 1

And finally the Assignment update! The link for Assignment 2 is here. At first, when my partner and I started reading the assignment, it seemed a bit complicated, especially since trees were a new concept to us. We were confused about why we’d need multiple classes represent the trees, however, after a bit more reading and coding, we found it actually made things a lot easier if we made classes for each different type of regex, and using a Regex superclass which we could inherit __init__ and __eq__method, and then simply write out the __repr__ method for each class (since each one would start differently, inheritance wouldn’t be effective here).

That’s pretty much it for this week!