Algorithms For Dummies

 

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Queues: A queue is a first in/first out (FIFO) collection. You use it to track 

items that need to be processed in some way. Think of a queue as a line at the 

bank. You go into the line, wait your turn, and are eventually called to talk with 

a teller.

 

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Deques: A double-ended queue (deque) is a queue-like structure that lets you 

add or remove items from either end, but not from the middle. You can use a 

deque as a queue or a stack or any other kind of collection to which you’re 

adding and from which you’re removing items in an orderly manner (in 

contrast to lists, tuples, and dictionaries, which allow randomized access and 

management).

Of all the sequences, lists are the easiest to understand and are the most directly 

related to a real-world object. Working with lists helps you become better able to 

work with other kinds of sequences that provide greater functionality and 

improved  flexibility.  The  point  is  that  the  data  is  stored  in  a  list  much  as  you 

would write it on a piece of paper: One item comes after another. The list has a 

beginning, a middle, and an end. Python numbers the items in the list. (Even if 

you might not normally number the list items in real life, using a numbered list 

makes the items easy to access.) To see how you can work with lists, start a copy 

of IPython and type the following code:

ListA = [0, 1, 2, 3]

ListB = [4, 5, 6, 7]

ListA.extend(ListB)

ListA

When you type the last line of code, you see the output of 

[0, 1, 2, 3, 4, 5, 

6, 7]

. The 

extend()

 function adds the members of 

ListB

 to 

ListA

. Besides extend-

ing lists, you can also add to them by using the 

append()

 function. Type ListA.