repr$($node$1)$ instead of node$1.\_-()$

$x+y$ instead of $x*.\_$ add$\_-($y$)$

object$1==$ object$2$ instead of object$1.($object$2)$

len$($collection$)$ instead of collection.

This applies to test cases and functionality within a class. The magic syntax is preferred because it improves

readability. The only common exception is when calling super$().\_-.$

Part $2-$ class LinkedList

In the same files as above, but in different classes $($LinkedList and TestLinkedList$),$ implement the

LinkedList class as described below.

LinkedList

head: Node $|$ None

$\_$tail: Node $|$ None

len: int

init $($self$,$ items: Optional$[$Iterable$[$Any$]])->$ None

Len $($self$)->$ int

get$\_$head$($self$)->$ Any $|$ None

get$\_$tail$($self$)->$ Any $|$ None

add$\_$last$($self$,$ item: Any$)->$ None

add$\_$first$($self$,$ item: Any$)->$ None

remove$\_$last$($self$)->$ Any

remove$\_$first$($self$)->$ Any

Figure $2$: Class diagram for LinkedList. Note that items in LinkedList. is an optional paramter

$($it defaults to None, and it can be any iterable if included. This means lists, tuples, sets, dictionaries, strings,

or even the range object are fair game.$)$

init$($self$,$ items: Optional $[$Iterable$[$Any$])->$ None

optional collection items are sequentially added to LinkedList if included

use add$\_$last $()$ to add items in correct order

get$\_$head$($self$)$ Any I None

Returns item stored in self $.\_$head, or None for an empty LinkedList

get$\_$tail$($self$)$ Any I None

Returns item stored in self $.\_$tail, or None for an empty LinkedList

add$\_$first$($self$,$ item: Any$)->$ None

adds a node to the front of the LinkedList with item

add$\_$last$($self$,$ item: Any$)->$ None

adds a node to the end of the LinkedList with item

remove$\_$first$($self$)->$ Any

removes first node from LinkedList and returns its item

raises a RuntimeError if LinkedList is empty when called

remove$\_$last$($self$)-->$ Any

removes last node from LinkedList and returns its item

raises a RuntimeError if LinkedList is empty when called

Flow:

Empty initialization

Red: test$\_$linkedlist.py$,$ TestLinkedList class:

Create empty LinkedList e$.$g$.$ LL$1=$ LinkedList$()$

Assert length is correct $($should be $0)$

Assert get$\_$head$()$ and get$\_$tail$()$ return correct values $($should be None$)$

Green:

linkedlist.py$,$ LinkedList class:

Implement $\_-\_,-,$ get$\_$head$(),$ and get$\_$tail$()$

add$\_$last

Red: test$\_$linkedlist.py$,$ TestLinkedList class:

Create an empty LinkedList

Using a for loop, sequentially add items to end of LinkedList. With each add, assert that

you get the correct values from:

$**$ len $()$

get$\_$head$()$

get$\_$tail$()$

$,$ Green:

linkedlist.py$,$ LinkedList class:

Implement add$\_$last

Non$-$empty initialization

Red: test$\_$linkedlist.py$,$ TestLinkedList class:

initialize a new linked list with some iterable, e$.$g$.$:

LL$1=$ LinkedList $([\text{'}$a$\text{'},\text{'}$b$\text{'},\text{'}$c$\text{'}])$

LL$1=$ LinkedList $($range $(10))$

Test you get correct values from len, get$\_$head$(),$ and get$\_$tail$()$

Green:

linkedlist.py$,$ LinkedList class:

Finish implementing $\_$

See note on default parameters below

add$\_$first

Test similar to add$\_$last

Implement

remove$\_$first

Red: test$\_$linkedlist.py$,$ TestLinkedList class:

Build up a linked list $($either create a non$-$empty list, or use add$\_$first or add$\_$last$)$

Iteratively call remove$\_$first$()$ until the LinkedList is empty. With every remove$\_$first$()$

call, assert you get correct values from:

remove$\_$first $()($should return item in first node$)$