I am working out of How To Think Like A Computer
Scientist. I am on the chapter that covers linked
queues. Here is some code that creates a linked queue
class:
class Queue:
def __init__(self):
self.length = 0
self.head = None
def isEmpty(self):
return (self.length == 0)
def insert(self, cargo):
node = Node(cargo)
node.next = None
if self.head == None:
# if list is empty the new node goes first
self.head = node
else:
# find the last node in the list
last = self.head
while last.next:
last = last.next
# append the new node
last.next = node
self.length = self.length + 1
def remove(self):
cargo = self.head.cargo
self.head = self.head.next
self.length = self.length - 1
return cargo
The node is defined by:
class Node:
def __init__(self, cargo=None, next=None):
self.cargo = cargo
self.next = next
def __str__(self):
return str(self.cargo)
I am confused by the insert class. I am not quite
sure how it works. More to the point, I am not sure
if it works:
>>> from linked_queue import *
>>> queue = Queue()
>>> queue.isEmpty()
True
>>> queue.insert("cargo")
>>> print queue.head
cargo
>>> print queue.length
1
>>> queue.insert("more_cargo")
>>> print queue.length
2
>>> print queue.head
cargo
Where is my second node? How can I access it?
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